Phyllosphere methylotrophs and climate resilience: The emerging role of PPFMS in mitigating abiotic stresses

Introduction

The expansion of the global human population is a principal factor instigating planetary-scale transformations, including biodiversity decline, ozone layer erosion, and climatic shifts. This demographic trend profoundly influences climate patterns, a situation exacerbated by the widespread application of chemical fertilizers. The primary impacts on flora include alterations to essential physiological processes that are sensitive to climate. Through secondary pathways, a changing climate disrupts the nuanced symbiotic and pathogenic relationships plants maintain with organisms like insects and microbes. Plant development and vitality are highly responsive to environmental conditions, making them vulnerable to both living (biotic) and non-living (abiotic) stressors. The latter category comprises extremes in temperature, inadequate or excessive light and solar radiation, water scarcity or flooding, nutrient imbalances, soil salinity, and atmospheric pollution (Patel et al., 2017, 2018; Gopi et al., 2020) [45,44,15] . Among these, drought stands out as a major peril to agricultural sustainability and plant health on a global scale. Confronting these issues to safeguard worldwide food supplies demands an urgent focus on innovating new cultivation methods and integrating agricultural practices that are resilient to climate variability. This situation calls for a fundamental strategic shift in farming systems to both alleviate and adjust to the detrimental consequences of a warming planet. Abiotic stresses are a major threat to that depletes plant development, impedes seed germination, and diminishes crop yields. Research indicates that microorganisms which promote plant growth are vital biological tools for climate change mitigation (Kabiraj et al., 2020; Krishnamoorthy et al., 2021) [23,26] . The microbial world has diverse roles; for instance, methanogens in environments like wetlands and ruminant digestive systems release methane, whereas methylotrophs consume it as a carbon source, thereby reducing its atmospheric concentration. Beneficial microbes associated with plants have recently gained significant interest for their capacity to boost agricultural output and confer resilience against environmental stresses (Gopi et al., 2020; Rani et al., 2021) [15, 51] . Plant Growth-Promoting Bacteria (PGPB), support plants through direct and indirect strategies. These include nitrogen fixation, phytohormone synthesis, improved micronutrient absorption, and the secretion of bioactive compounds such as siderophores, antibiotics, and enzymes that suppress pathogens and enhance soil structure (Pérez-Flores et al., 2017; Prittesh et al., 2020) [46,50] . Collectively, these Plant Growth Promotion (PGP) activities are fundamental to advancing ecosystem health and securing agricultural productivity.

Methylotrophs

Methylotrophs are a class of microorganisms characterized by their unique metabolic ability to use single-carbon (C1) molecules for growth and energy. A principal natural environment for these methanol-consuming bacteria is the phyllosphere, or leaf surface, which hosts substantial populations from genera such as Methylobacterium, Methylophilus, Methylibium and Hyphomicrobium. The prevalence of methanol, a by-product of plant pectin metabolism, on leaves offers a competitive niche for these specialized bacteria (Sy et al., 2005) [64] . The composition of this leaf-dwelling microbial community is influenced by multiple factors, with plant genetics and geographical location being the most significant drivers (Vorholt, 2012) [68] . While chemical fertilizers can boost plant growth and yield, their residual presence disrupts natural ecosystems. As a sustainable alternative, methylotrophs residing in the phyllosphere show great promise as bioinoculants. These bacteria can promote plant development by modifying plant physiology, secreting growth hormones, and alleviating biotic and abiotic stresses. Their application aligns with the principles of organic farming and presents a solution to the rising costs, environmental damage, and food safety concerns linked to synthetic fertilizers. Consequently, microbial biofertilizers are increasingly recognized as a viable strategy for enhancing crop yield and quality within sustainable agricultural frameworks (Ryu et al., 2006) [52] . Foliar application of such biofertilizers is particularly effective, as it bypasses the limiting factors often present in the soil environment. Methylotrophs are ubiquitous, non-pathogenic bacteria that thrive on methanol and other compounds. Their metabolic versatility and rapid growth under varying conditions underscore their significant biotechnological potential. As phytosymbionts, their ability to produce plant-growth regulators like cytokinins, auxins, and vitamins further enhances their agricultural value. Genomic studies reveal that these methylotrophs possess a suite of genes that enable survival on plant surfaces, including defenses against UV radiation, oxidative stress, and desiccation, as well as genes for motility and signaling (Kwak et al., 2014) [29] . Inoculation with Methylobacterium has been demonstrated to improve plant health by modulating stress responses, such as lowering stress-induced ethylene levels and elevating pathogen-related proteins (Table 1). [31] Wheat Methylobacterium sp. Phyllosphere (Leaves) Production of Cytokinin class phytohormones (Meena et al., 2012) [39] Rice Methylobacterium sp. Rhizosphere (Root zone) Biological Nitrogen Fixation (N₂ Fixation) (Madhaiyan et al., 2006) [31] Red Pepper Methylobacterium suomiense Rhizosphere (Root zone) Enhanced root colonization and establishment (Sivakumar et al., 2017) [60] Tomato Methylobacterium suomiense Rhizosphere (Root zone) Enhanced root colonization and establishment (Sivakumar et al., 2017) [60] Sugarcane Methylobacterium sp. Rhizosphere (Root zone)

Indole-3-acetic acid (IAA) synthesis and other Plant Growth-Promoting (PGP) activities (Sathyan et al., 2018) [55] Soybean Pink-Pigmented Facultative Methylotrophs (PPFMs) Phyllosphere (Leaves) Synthesis of the phytohormone Indole-3-acetic acid (IAA) (Sivakumar et al., 2017) [60] Groundnut Pink-Pigmented Facultative Methylotrophs (PPFMs) Phyllosphere (Leaves) Synthesis of the phytohormone Indole-3-acetic acid (IAA) (Sivakumar et al., 2017) [60] Mung Bean Methylobacterium organophilum Mud (Soil substrate) Application as a Bio-fertilizer to enhance plant growth (Collet et al., 2015) [7] Green Gram Pink-Pigmented Facultative Methylotrophs (PPFMs) Phyllosphere (Leaves) Application as a Bio-fertilizer to enhance plant growth (Sivakumar et al., 2017) [60] Black pepper Pink-Pigmented Facultative Methylotrophs (PPFMs)

Phyllosphere and rhizosphere

Application as a plant growth promoter and drought stress mitigator ManjuBhargavi et al., 2024 [35] Bird's eye chilli Pink-Pigmented Facultative Methylotrophs (PPFMs) Phyllosphere Application as a plant growth promoter and drought stress mitigator JasnaSherin et al., 2025 [19] Pink pigmented facultative methylotrophs (PPFMs) Pink pigmented facultative methylotrophs (PPFMs), a distinct subgroup within methylotrophic bacteria, are of significant physiological interest. Bacteria of the genus Methylobacterium demonstrate a notable capacity to withstand extreme environmental challenges, such as desiccation, freezing, exposure to chlorine and various forms of radiation, and high temperatures (Trotsenko et al.,

2001) [67] . These strictly aerobic, Gram-negative, rod-shaped α-Proteobacteria typically engage in a symbiotic relationship with plants, predominantly colonizing the phyllosphere. Their metabolic versatility allows them to grow on single-carbon substrates like methanol and methylamine, in addition to multi-carbon compounds (Chistoserdova et al., 2003) [6] . A defining trait is their pink pigmentation, which stems from carotenoids, mainly xanthophylls, and provides protection against intense light and radiation.

The diversity of PPFMs is reflected in their associations with various plant species. For example, Methylobacterium populi inhabits poplar tree tissues, M. nodulans forms nodules on the legume Crotalaria glaucoides, and M. goesingense is linked to the hyperaccumulator Thlaspi goesingense (Jourand et al., 2004) [22] . Other species, including M. extorquens and M. fujisawaense, are common inhabitants of the leaf surface on numerous plants. Methylotrophic bacteria, comprising a wide range of genera and species, are commonly associated with diverse plants. These bacteria colonize both leaf surfaces where they can constitute 14-20% of the microbial population in temperate climates and soil or root zones where methanol is present (Delmotte et al., 2009) [9] . Their ability to metabolize methanol via specialized oxidative pathways distinguishes them ecologically. Evidence of their broad distribution includes isolates from internal poplar tissues, different anatomical parts of sunflowers (Schauer and Kutschera, 2008), and the phyllosphere of several crops. The plant growth-promoting capabilities of Methylobacterium are multifaceted. They can fix atmospheric nitrogen, solubilize phosphates, and lower plant ethylene levels via the enzyme ACC deaminase, thereby enhancing stress tolerance and growth (Jourand et al., 2004; Madhaiyan et al., 2006) [22,31] . They also contribute to induced systemic resistance against pathogens. Manish et al. (2016) [34] reported their importance in sustainable agriculture, noting their critical function in soil biogeochemical cycles. They improve air quality by metabolizing volatile organic compounds and are integral to the global cycling of carbon, nitrogen, and phosphorus, potentially helping to mitigate climate change. Consequently, both rhizospheric and phyllospheric methylotrophs are increasingly deployed as eco-friendly and cost-effective bioinoculants, serving as alternatives to synthetic fertilizers. Their application improves plant water status, boosts photosynthetic efficiency, and elevates the concentration of protective osmolytes like proline and antioxidant enzymes such as catalase, thereby strengthening the plant's defense against abiotic stress.

Plant growth promotion by PPFMs

Extreme biotic and abiotic stresses are major constraints to plant growth and productivity. Numerous studies have demonstrated that methylotrophs exhibit plant growthpromoting (PGP) traits under adverse conditions. Research on Methylobacterium has revealed multiple PGP mechanisms, including the synthesis of phytohormones such as indole-3-acetic acid (IAA), gibberellins, and cytokinins, which enhance root and shoot development and increase overall plant biomass (Lidstrom and Chistoserdova, 2002; Grossi et al., 2020) [30,16] . PPFMs establish symbiotic associations with plants, particularly in the rhizosphere, and serve as a source of bioactive compounds for plant protection. They also harbor polyketide synthases and demonstrate resistance to harmful UV radiation. Inoculation with PPFMs has been shown to improve the growth and yield of crops such as rice and soybean by promoting nitrogen fixation, solubilizing mineral phosphate, and inducing systemic resistance against pathogens (Fig. 1.). [47,48] . Both epiphytic and endophytic methylotrophs contribute directly to plant growth by producing phytohormones, 1aminocyclopropane-1-carboxylic acid (ACC) deaminase, siderophores, secondary metabolites, hydrogen cyanide, and extracellular hydrolytic enzymes. These compounds, together with antagonistic substances, play key roles in safeguarding plants against pathogens and mitigating environmental stress (Subhaswaraj et al., 2017; Yadav and Yadav, 2018) [62,69] . Beneficial effects of Methylobacterium application have been demonstrated in several crops including wheat (Poonguzhali et al., 2007) [47] , barnyard millet (Echinochloa frumentacea Var. COKV 2), biodiesel plant Crambe abyssinica, ginger, rice, cotton, and cardamom. These studies collectively highlight the diverse interactions between Methylobacterium and host plants. Due to their multiple plant growth-promoting traits, PPFMs are considered promising bioinoculants in sustainable agriculture.

Classified as biosafety level one organisms, Methylobacterium species are non-pathogenic and safe for agricultural applications. Based on their beneficial features, several Methylobacterium based biofertilizers have been commercialized. For example, NewLeaf Symbiotics developed a bioproduct consisting solely of Methylobacterium strains to promote the growth of cotton, tomato, peanut, rice, corn, soybean, and wheat. Despite their potential, only a few commercial formulations are available. Recently, innovative technologies such as seed coatings using immobilized cells of Methylorubrum aminovorans in chitosan-polyvinyl alcohol nanofiber matrices have been introduced to improve cotton seed quality.

Abiotic stress and plant health

Plant health and agricultural yield are primarily limited by abiotic stress factors on a global scale. These non-living challenges, which include extremes of temperature, drought, flooding, soil salinity, and contamination from heavy metals such as cadmium, copper, and mercury, significantly disrupt fundamental physiological processes (Zhang et al., 2009; Hussain et al., 2020) [70,20] . Specifically, heavy metal pollution can impair essential functions like photosynthesis, respiration, and nutrient assimilation. The impact of temperature is particularly deleterious. High temperatures induce photooxidation and a surge in reactive oxygen species (ROS), leading to protein denaturation and aggregation, which culminates in cell death (Fig 2 .). On the other hand, low temperatures alter membrane fluidity, slow metabolic rates, and inhibit enzymatic activity, severely compromising plant growth and potentially reducing crop yields by as much as 50% (Theocharis et al., 2012) [65] . [18] . Furthermore, solar radiation can cause direct damage to genetic material (DNA), leading to heritable abnormalities and reduced viability in subsequent generations (Cavinato et al., 2017) [4] . PPFMs have been demonstrated to enhance plant resilience. Methylobacterium oryzae can protect rice from salinity stress, while they aid tomato plants in withstanding drought (Chanratana et al., 2017) [5] . Similarly, the successful colonization of rhizospheric Methylobacterium mesophilicum has been observed in tomatoes under salinity stress and in cucumbers under drought conditions, underscoring its potential role in stress alleviation (Egamberdieva et al., 2015) [10] .

Abiotic stress management mediated by methylotrophs

PPFMs play a crucial role in enhancing plant resilience against diverse environmental stresses, including drought, salinity, and heavy metal toxicity. This ability is largely attributed to their production of metabolites that trigger stress-resistance responses. PPFMs possess adaptive mechanisms that allow them to endure challenging conditions in the rhizosphere and soil environments. Under drought stress, they promote plant tolerance through the synthesis of osmoprotectants and antioxidants osmoprotectants maintain cellular water balance, while antioxidants mitigate reactive oxygen species (ROS) damage. In saline conditions, PPFMs contribute to plant adaptation by producing compounds such as proline and glycine betaine, which stabilize osmotic balance and prevent ionic toxicity. Moreover, certain PPFM strains can tolerate and detoxify heavy metals by sequestering and immobilizing them within their cells, thereby reducing their harmful effects on plants and soil ecosystems. These bacteria also thrive across broad temperature and pH ranges, enabling survival and function in diverse and fluctuating environments.

Drought stress

Drought stress severely impacts global crop production, forcing plants to rely on their internal metabolic mechanisms for adaptation. Water deficit reduces turgor pressure, limits cell division and expansion, and disrupts photosynthesis by lowering pigment content and altering hormonal balance and osmotic regulation (Silva et al., 2020) [58] . Studies indicate that plant growth-promoting regulators can partly alleviate such abiotic stress effects (Saikia et al., 2018; Yadav and Yadav, 2018; Filgueiras et al., 2020) [54,69,13] . Drought stress causes substantial yield losses in crops such as rice, pea, and alfalfa by reducing germination, shoot-root growth, and overall vigor (Manickavelu et al., 2006) [31] . Limited water availability disturbs osmotic balance, elevating reactive oxygen species and ethylene levels, which damage cellular components and impair energy metabolism (Priestley, 1986; Farooq et al., 2009) [49,12] . PPFMs counteract these effects by boosting catalase activity and improving stress tolerance indices. PPFMs have been shown to enhance seed germination and mitigate drought effects through foliar applications (Sivakumar et al., 2017) [60] . Similarly, several methylotrophs isolated from long-stored paddy soils exhibit drought resilience (Collet et al., 2015) [7] . Foliar or root application of PPFMs enhances the growth of tomato and wheat under drought conditions through modulation of phytohormone synthesis. Methylobacterium oryzae and related species M. mesophilicum, M. fujisawaense and M. radiotolerans have also been documented to colonize plant tissues and enhance cytokinin levels, thereby improving plant survival under drought stress (Egamberdieva et al., 2015; Sathyan et al., 2018) [10,55] .

Salinity stress

Soil salinity is a major global constraint on agricultural productivity, affecting about one billion hectares across nearly 100 countries. In India, around 20% of irrigated land is becoming saline due to continuous irrigation with salt-rich water (Mann et al., 2020; Sahab et al., 2021) [36,53] . Excessive soil salts induce stress in plants, suppress growth, and may lead to crop failure, making salinity a critical abiotic stress in arid and semi-arid regions (Mishra et al., 2016) [41] . High salinity at any growth stage especially early development impairs nutrient absorption, hinders root growth, and lowers germination (Sorty et al., 2016) [61] . Accumulated sodium ions in chloroplasts disrupt photosystem II and electron transport, reducing photosynthetic efficiency and causing oxidative stress through excess ROS, which triggers membrane damage and early leaf senescence (Hameed et al., 2021) [17] . While plants have inherent stress resistance systems, beneficial microbes enhance tolerance by inducing stress-responsive genes, antioxidants, and osmolyte accumulation (Meena et al., 2017; Kumar and Verma, 2018) [40,27] . A methylotrophic actinobacterium, Nocardioides, isolated from fresh soybean leaves, has been shown to enhance wheat growth under saline stress (Meena et al., 2020) [38] . Methlylophaga lonarensis from Lonar Lake sediments (Antony et al., 2012) [2] , Methlylophaga muralis from soda lake brine (Shmareva et al., 2018) [57] , and Methyloligella halotolerans gen. nov., sp. nov. from saline habitats of the Ural region demonstrated tolerance ranges between 0.5%-2.0% and up to 16.0% NaCl (w/v). Methylobacterium mesophilicum isolated from wheat roots tolerated up to 6.0% NaCl and continued producing indole-3-acetic acid (IAA) under 4.0% NaCl conditions (Egamberdieva et al., 2015) [10] .

Heavy metals stress

Heavy metals released from industrial activities represent a major threat to agriculture and human health (Glick, 2010). Common contaminants like zinc (Zn), cadmium (Cd), copper (Cu), chromium (Cr), arsenic (As), nickel (Ni), and lead (Pb) frequently accumulate in soils (Khan et al., 2008) [24] . Their bioaccumulation disrupts food chains and reduces crop yield. Although some plants can extract metals from polluted soils, excess concentrations impair metabolism, causing oxidative stress, DNA and cellular damage, osmotic imbalance, and declines in photosynthesis, respiration, and protein synthesis all of which hinder growth and reproduction (Fatima et al., 2021) [11] . Plant-microbe interactions offer a sustainable strategy for remediating metal-contaminated soils. These interactions detoxify hazardous ions through uptake, immobilization, mobilization, and biotransformation, where metals undergo chemical alteration via microbial metabolic activity (Tiwari et al., 2017; Afsal et al., 2020) [66,11] . Among plant growthpromoting bacteria, methylotrophs show remarkable potential in mitigating heavy metal toxicity. Methylobacterium oryzae CBM20, isolated from rice, reduced Ni and Cd stress while promoting tomato growth (Madhaiyan et al., 2007) [32] . Similarly, Methylobacterium sp. AF-M from Acacia farnesiana enhanced arsenate tolerance (Alcántara-Martínez et al., 2018) [3] , and M. hispanicum EM2 from mine tailing soil exhibited lead resistance up to 800 mg L⁻¹ (Jeong et al., 2019) [21] . M. fujisawanense CT4 and M. goesingense from Thlaspi goesingense demonstrated tolerance to Zn, Ni, and Cd (Kunito et al., 1997) [28] .

Importance of PPFMs in sustainable agriculture

Sustainable agriculture aims to balance food security with the responsible management of natural resources, and PPFM play a vital role in achieving this goal. By solubilizing nutrients such as phosphorus and iron, PPFM improve soil fertility and reduce reliance on synthetic fertilizers, minimizing both costs and environmental pollution. Their ability to enhance nutrient uptake and promote plant hormone production supports healthier, disease-resistant crops and decreases pesticide use. PPFM also regulate stomatal conductance, improving water-use efficiency and drought resilience key aspects of climate-adaptive farming. Additionally, they enrich rhizospheric microbial diversity, strengthen soil structure, and enhance nutrient cycling, contributing to long-term soil health. Integrating PPFM into sustainable practices not only promotes ecosystem conservation but also offers economic gains through reduced inputs and improved yields. PPFMs play a vital ecological role across diverse habitats due to their unique metabolic abilities and interactions with the environment. As active participants in the global methane cycle, they oxidize methane a potent greenhouse gas-into carbon dioxide, thereby mitigating methane emissions and contributing to climate regulation and the carbon cycle. Several PPFM strains also possess the capacity to biodegrade aromatic and methylated pollutants, transforming them into less toxic or harmless compounds. This biodegradation potential is essential for bioremediation efforts aimed at restoring contaminated environments. Additionally, certain PPFMs exhibit antagonistic effects against plant pathogens, supporting plant health and reducing the need for chemical pesticides, thus promoting eco-friendly pest management. Overall, PPFMs contribute significantly to nutrient cycling, greenhouse gas regulation, and environmental restoration, reinforcing their importance for ecosystem sustainability, agricultural productivity, and global environmental preservation.

Conclusion

Confronting the immense pressure of climate change and population growth necessitates a strategic shift away from input-intensive agriculture. This review underscores that abiotic stresses including drought, salinity, and heavy metal contamination are primary constraints on global food security. In this context, Pink Pigmented Facultative Methylotrophs (PPFMs) emerge as a powerful, sustainable bio-solution. These bacteria, native to plant surfaces, directly promote growth by producing phytohormones, fixing nitrogen, and solubilizing nutrients. Crucially, they are instrumental in building plant resilience. They alleviate abiotic stress by modulating stress ethylene, enhancing antioxidant defense, and accumulating protective osmolytes, thereby mitigating the damaging effects of drought, salinity, and toxic metals. Integrating PPFMs into agricultural practice aligns with the core goals of sustainable farming: reducing synthetic fertilizer and pesticide use, improving soil health, and enhancing water-use efficiency. Their proven role in promoting crop yield and stress tolerance, coupled with their safety and environmental benefits, positions PPFM bioinoculants as a cornerstone for developing climate-resilient and productive agricultural systems for the future.

Acknowledgement

AcknowledgementI would like to express my gratitude towards the co-authors of this article and the peer reviewers for their valuable comments and suggestions. I also support the editorial team's guidance and support throughout the publication process.

References

1. Afsal F, Majumdar A, Kumar JS, Bose S. Microbial inoculation to alleviate the metal toxicity in crop plants and subsequent growth promotion. In: Sustainable solutions for elemental deficiency and excess in crop plants. Singapore: Springer Singapore; 2020. p. 451479.
2. Antony CP, Doronina NV, Boden R, Trotsenko YA, Shouche YS, Murrell JC. Methylophaga lonarensis sp. nov., a moderately haloalkaliphilic methylotroph isolated from the soda lake sediments of a meteorite impact crater. International Journal of Systematic and Evolutionary Microbiology. 2012;62(Pt 7):1613-1618.
3. Alcántara-Martínez N, Figueroa-Martínez F, RiveraCabrera F, Gutiérrez-Sánchez G, Volke-Sepúlveda T. An endophytic strain of Methylobacterium sp. increases arsenate tolerance in Acacia farnesiana (L.) Willd: a proteomic approach. Science of the Total Environment. 2018;625:762-774.
4. Cavinato M, Waltenberger B, Baraldo G, Grade CV, Stuppner H, Jansen-Dürr P. Plant extracts and natural compounds used against UVB-induced photoaging. Biogerontology. 2017;18(4):499-516.
5. Chanratana M, Han GH, Roy Choudhury A, Sundaram S, Halim MA, Krishnamoorthy R, et al. Assessment of Methylobacterium oryzae CBMB20 aggregates for salt tolerance and plant growth promoting characteristics for bio-inoculant development. AMB Express. 2017;7(1):208.
6. Chistoserdova L, Chen SW, Lapidus A, Lidstrom ME. Methylotrophy in Methylobacterium extorquens AM1 from a genomic point of view. Journal of Bacteriology. 2003;185(10):2980-2987.
7. Collet S, Reim A, Ho A, Frenzel P. Recovery of paddy soil methanotrophs from long term drought. Soil Biology and Biochemistry. 2015;88:69-72.
8. Dary M, Chamber-Pérez MA, Palomares AJ, Pajuelo E. "In situ" phytostabilisation of heavy metal polluted soils using Lupinus luteus inoculated with metal resistant plant-growth promoting rhizobacteria. Journal of Hazardous Materials. 2010;177(1-3):323-330.
9. Delmotte N, Knief C, Chaffron S, Innerebner G, Roschitzki B, Schlapbach R, et al. Community proteogenomics reveals insights into the physiology of phyllosphere bacteria. Proceedings of the National Academy of Sciences. 2009;106(38):16428-16433.
10. Egamberdieva D, Wirth S, Alqarawi AA, Abd_Allah E. Salt tolerant Methylobacterium mesophilicum showed viable colonization abilities in the plant rhizosphere. Saudi Journal of Biological Sciences. 2015;22(5):585590.
11. Fatima A, Farid M, Farid S, Ishaq HK, Iftikhar U, Rizwan M, et al. Heavy metals induced physiological and biochemical changes in fenugreek (Trigonella foenum-graceum L.). In: Approaches to the Remediation of Inorganic Pollutants. 2021. p. 239-258.
12. Farooq M, Wahid A, Kobayashi NSMA, Fujita DBSMA, Basra SM. Plant drought stress: effects, mechanisms and management. In: Sustainable Agriculture. Dordrecht: Springer Netherlands; 2009. p. 153-188.
13. Filgueiras L, Silva R, Almeida I, Vidal M, Baldani JI, Meneses CHSG. Gluconacetobacter diazotrophicus mitigates drought stress in Oryza sativa L. Plant and Soil. 2020;451(1-2):57-73.
14. Glick BR. Using soil bacteria to facilitate phytoremediation. Biotechnology Advances. 2010;28(3):367-374.
15. Gopi K, Jinal HN, Prittesh P, Kartik VP, Amaresan N. Effect of copper-resistant Stenotrophomonas maltophilia on maize (Zea mays) growth, physiological International Journal of Advanced Biochemistry Research https://www.biochemjournal.com properties, and copper accumulation: potential for phytoremediation into biofortification. International Journal of Phytoremediation. 2020;22(6):662-668.
16. Grossi CEM, Fantino E, Serral F, Zawoznik MS, Fernandez Do Porto DA, Ulloa RM. Methylobacterium sp. 2A is a plant growth-promoting rhizobacteria that has the potential to improve potato crop yield under adverse conditions. Frontiers in Plant Science. 2020;11:71.
17. Hameed A, Ahmed MZ, Hussain T, Aziz I, Ahmad N, Gul B, et al. Effects of salinity stress on chloroplast structure and function. Cells. 2021;10(8):2023.
18. Han P, Wang ZJ, Lavoir AV, Michel T, Seassau A, Zheng WY, et al. Increased water salinity applied to tomato plants accelerates the development of the leaf miner Tuta absoluta through bottom-up effects. Scientific Reports. 2016;6(1):32403.
19. Jasna Sherin PT, Anu Rajan S, Anith KN, Anuradha T, Soni KB, Soumya VI, et al. Functional pink pigmented facultative methylotrophs from Capsicum frutescens phyllosphere as bioinoculants for growth promotion and drought stress alleviation in chilli. Journal of Crop Health. 2025;77(5):160-169.
20. Hussain S, Khaliq A, Noor MA, Tanveer M, Hussain HA, Hussain S, et al. Metal toxicity and nitrogen metabolism in plants: an overview. In: Carbon and Nitrogen Cycling in Soil. 2019. p. 221-248.
21. Jeong SW, Kim HK, Yang JE, Choi YJ. Removal of Pb(II) by pellicle-like biofilm-producing Methylobacterium hispanicum EM2 strain from aqueous media. Water. 2019;11(10):2081.
22. Jourand P, Giraud E, Bena G, Sy A, Willems A, Gillis M, et al. Methylobacterium nodulans sp. nov., for a group of aerobic, facultatively methylotrophic, legume root-nodule-forming and nitrogen-fixing bacteria. International Journal of Systematic and Evolutionary Microbiology. 2004;54(6):2269-2273.
23. Kabiraj A, Majhi K, Halder U, Let M, Bandopadhyay R. Role of plant growth-promoting rhizobacteria (PGPR) for crop stress management. In: Sustainable Agriculture in the Era of Climate Change. Cham: Springer International Publishing; 2020. p. 367-389.
24. Khan S, Cao Q, Zheng YM, Huang YZ, Zhu YG. Health risks of heavy metals in contaminated soils and food crops irrigated with wastewater in Beijing, China. Environmental Pollution. 2008;152(3):686-692.
25. Koini MA, Alvey L, Allen T, Tilley CA, Harberd NP, Whitelam GC, et al. High temperature-mediated adaptations in plant architecture require the bHLH transcription factor PIF4. Current Biology. 2009;19(5):408-413.
26. Krishnamoorthy R, Anandham R, Senthilkumar M, Venkatramanan V. Adaptation mechanism of methylotrophic bacteria to drought condition and its strategies in mitigating plant stress caused by climate change. In: Exploring Synergies and Trade-Offs Between Climate Change and the Sustainable Development Goals. Singapore: Springer Singapore; 2020. p. 145-158.
27. Kumar A, Verma JP. Does plant-microbe interaction confer stress tolerance in plants: a review? Microbiological Research. 2018;207:41-52.
28. Kunito T, Shibata S, Matsumoto S, Oyaizu H. Zinc resistance of Methylobacterium species. Bioscience, Biotechnology, and Biochemistry. 1997;61(4):729-731.
29. Kwak MJ, Jeong H, Madhaiyan M, Lee Y, Sa TM, Oh TK, et al. Genome information of Methylobacterium oryzae, a plant-probiotic methylotroph in the phyllosphere. PLoS One. 2014;9(9):e106704.
30. Lidstrom ME, Chistoserdova L. Plants in the pink: cytokinin production by Methylobacterium. Journal of Bacteriology. 2002;184(7):1818.
31. Madhaiyan M, Poonguzhali S, Ryu J, Sa T. Regulation of ethylene levels in canola (Brassica campestris) by 1aminocyclopropane-1-carboxylate deaminasecontaining Methylobacterium fujisawaense. Planta. 2006;224(2):268-278.
32. Madhaiyan M, Poonguzhali S, Sa T. Metal tolerating methylotrophic bacteria reduces nickel and cadmium toxicity and promotes plant growth of tomato (Lycopersicon esculentum L.). Chemosphere. 2007;69(2):220-228.
33. Manickavelu A, Nadarajan N, Ganesh SK, Gnanamalar RP, Chandra Babu R. Drought tolerance in rice: morphological and molecular genetic consideration. Plant Growth Regulation. 2006;50(2):121-138.
34. Manish Kumar MK, Tomar RS, Harshad Lade HL, Paul D. Methylotrophic bacteria in sustainable agriculture. 2016.
35. Manju Bhargavi Y, Rajan SA, Chitra N, Soumya VI, Beena R, Anith KN. Pink pigmented facultative methylotrophs (PPFMs) improve rooting in black pepper (Piper nigrum L.) cuttings and mitigate drought stress. Plant Science. 2024;11:1-10.
36. Mann A, Kumar A, Sanwal SK, Sharma PC. Sustainable production of pulses under saline lands in India. In: Legume Crops-Prospects, Production and Uses. London: IntechOpen; 2020.
37. Mapelli F, Marasco R, Balloi A, Rolli E, Cappitelli F, Daffonchio D, et al. Mineral-microbe interactions: biotechnological potential of bioweathering. Journal of Biotechnology. 2012;157(4):473-481.
38. Meena KK, Bitla UM, Sorty AM, Singh DP, Gupta VK, Wakchaure GC, et al. Mitigation of salinity stress in wheat seedlings due to the application of phytohormone-rich culture filtrate extract of methylotrophic actinobacterium Nocardioides sp. NIMMe6. Frontiers in Microbiology. 2020;11:2091.
39. Meena KK, Kumar M, Kalyuzhnaya MG, Yandigeri MS, Singh DP, Saxena AK, et al. Epiphytic pinkpigmented methylotrophic bacteria enhance germination and seedling growth of wheat (Triticum aestivum) by producing phytohormone. Antonie Van Leeuwenhoek. 2012;101(4):777-786.
40. Meena KK, Sorty AM, Bitla UM, Choudhary K, Gupta P, Pareek A, Minhas PS. Abiotic stress responses and microbe-mediated mitigation in plants: the omics strategies. Frontiers in Plant Science. 2017;8:172.
41. Mishra BK, Meena KK, Dubey PN, Aishwath OP, Kant K, Sorty AM, Bitla UM. Influence on yield and quality of fennel (Foeniculum vulgare Mill.) grown under semi-arid saline soil, due to application of native phosphate solubilizing rhizobacterial isolates. Ecological Engineering. 2016;97:327-333.
42. Bacillus spp. strains ameliorate drought stress in maize by a strain-specific antioxidant response modulation. Microorganisms. 2020;8(6):823.
43. Munns R, James RA, Läuchli A. Approaches to increasing the salt tolerance of wheat and other cereals. Journal of Experimental Botany. 2006;57(5):10251043.
44. Patel DH, Naik JH, Amaresan N. Synergistic effect of root-associated bacteria on plant growth and certain physiological parameters of banana plant (Musa acuminata). Archives of Agronomy and Soil Science. 2018;64(7):1021-1031.
45. Patel S, Jinal HN, Amaresan N. Isolation and characterization of drought resistance bacteria for plant growth promoting properties and their effect on chilli (Capsicum annuum) seedling under salt stress. Biocatalysis and Agricultural Biotechnology. 2017;12:85-89.
46. Pérez-Flores P, Valencia-Cantero E, AltamiranoHernández J, Pelagio-Flores R, López-Bucio J, GarcíaJuárez P, et al. Bacillus methylotrophicus M4-96 isolated from maize (Zea mays) rhizoplane increases growth and auxin content in Arabidopsis thaliana via emission of volatiles. Protoplasma. 2017;254(6):22012213.
47. Poonguzhali S, Madhaiyan M, Sa T. Production of acylhomoserine lactone quorum-sensing signals is widespread in gram-negative Methylobacterium. Journal of Microbiology and Biotechnology. 2007;17(2):226-231.
48. Poonguzhali S, Madhaiyan M, Yim WJ, Kim KA, Sa TM. Colonization pattern of plant root and leaf surfaces visualized by use of green-fluorescent-marked strain of Methylobacterium suomiense and its persistence in rhizosphere. Applied Microbiology and Biotechnology. 2008;78(6):1033-1043.
49. Priestley DA. Seed Aging: Implications for Seed Storage and Persistence in the Soil. Ithaca: Cornell University Press; 1986.
50. Prittesh P, Avnika P, Kinjal P, Jinal HN, Sakthivel K, Amaresan N. Amelioration effect of salt-tolerant plant growth-promoting bacteria on growth and physiological properties of rice (Oryza sativa) under salt-stressed conditions. Archives of Microbiology. 2020;202(9):2419-2428.
51. Rani V, Bhatia A, Kaushik R. Inoculation of plant growth promoting-methane utilizing bacteria in different N-fertilizer regime influences methane emission and crop growth of flooded paddy. Science of the Total Environment. 2021;775:145826.
52. Ryu CM, Hu CH, Reddy MS, Kloepper JW. Different signaling pathways of induced resistance by rhizobacteria in Arabidopsis thaliana against two pathovars of Pseudomonas syringae. New Phytologist. 2003;160(2):413-420.
53. Sahab S, Suhani I, Srivastava V, Chauhan PS, Singh RP, Prasad V. Potential risk assessment of soil salinity to agroecosystem sustainability: current status and management strategies. Science of the Total Environment. 2021;764:144164.
54. Saikia J, Sarma RK, Dhandia R, Yadav A, Bharali R, Gupta VK, et al. Alleviation of drought stress in pulse crops with ACC deaminase producing rhizobacteria isolated from acidic soil of Northeast India. Scientific Reports. 2018;8(1):3560.
55. Sathyan T, Mohanan AK, Dhanya MK, Aswathy TS, Preethy TT, Murugan M. Impact of pink pigmented facultative methylotrophic bacteria and synthetic materials on small cardamom (Elettaria cardamomum Maton.) under drought. Pharma Innovation Journal. 2018;7(1):1-4.
56. Schauer S, Kutschera U. A novel growth-promoting microbe, Methylobacterium funariae sp. nov., isolated from the leaf surface of a common moss. Plant Signaling & Behavior. 2011;6(4):510-515.
57. Shmareva MN, Doronina NV, Tarlachkov SV, Vasilenko OV, Trotsenko YA. Methylophaga muralis Bur 1, a haloalkaliphilic methylotroph isolated from the Khilganta soda lake (Southern Transbaikalia, Buryat Republic). Microbiology. 2018;87(1):33-46.
58. Silva R, Filgueiras L, Santos B, Coelho M, Silva M, Estrada-Bonilla G, et al. Gluconacetobacter diazotrophicus changes the molecular mechanisms of root development in Oryza sativa L. growing under water stress. International Journal of Molecular Sciences. 2020;21(1):333.
59. Singh BK, Bardgett RD, Smith P, Reay DS. Microorganisms and climate change: terrestrial feedbacks and mitigation options. Nature Reviews Microbiology. 2010;8(11):779-790.
60. Sivakumar R, Nandhitha GK, Chandrasekaran P, Boominathan P, Senthilkumar M. Impact of pink pigmented facultative methylotroph and PGRs on water status, photosynthesis, proline and NR activity in tomato under drought. International Journal of Current Microbiology and Applied Sciences. 2017;6(6):16401651.
61. Sorty AM, Meena KK, Choudhary K, Bitla UM, Minhas PS, Krishnani KK. Effect of plant growth promoting bacteria associated with halophytic weed (Psoralea corylifolia L.) on germination and seedling growth of wheat under saline conditions. Applied Biochemistry and Biotechnology. 2016;180(5):872-882.
62. Subhaswaraj P, Jobina R, Parasuraman P, Siddhardha B. Plant growth promoting activity of pink pigmented facultative methylotroph Methylobacterium extorquens MM2 on Lycopersicon esculentum L. Journal of Applied Biology and Biotechnology. 2017;5(1):42-46.
63. Sudhir P, Murthy SDS. Effects of salt stress on basic processes of photosynthesis. Photosynthetica. 2004;42(4):481-486.
64. Sy A, Giraud E, Jourand P, Garcia N, Willems A, De Lajudie P, et al. Methylotrophic Methylobacterium bacteria nodulate and fix nitrogen in symbiosis with legumes. Journal of Bacteriology. 2001;183(1):214220.
65. Theocharis A, Clément C, Barka EA. Physiological and molecular changes in plants grown at low temperatures. Planta. 2012;235(6):1091-1105.
66. Tiwari S, Prasad V, Chauhan PS, Lata C. Bacillus amyloliquefaciens confers tolerance to various abiotic stresses and modulates plant response to phytohormones through osmoprotection and gene expression regulation in rice. Frontiers in Plant Science. 2017;8:1510. International Journal of Advanced Biochemistry Research https://www.biochemjournal.com
67. Trotsenko YA, Ivanova EG, Doronina NV. Aerobic methylotrophic bacteria as phytosymbionts. Microbiology. 2001;70(6):623-632.
68. Vorholt JA. Microbial life in the phyllosphere. Nature Reviews Microbiology. 2012;10(12):828-840.
69. Yadav N, Yadav A. Biodiversity and biotechnological applications of novel plant growth promoting methylotrophs. Journal of Applied Biotechnology and Bioengineering. 2018;5(6):342-344.
70. Zhang E, Yin D, Xu L, Yang L, Yang K. Microstructure, mechanical and corrosion properties and biocompatibility of Mg-Zn-Mn alloys for biomedical application. Materials Science and Engineering C. 2009;29(3):987-993.