Psychrotolerance Mechanisms in Cold-Adapted Bacteria and their Perspectives as Plant Growth-Promoting Bacteria in Temperate Agriculture

Abstract

Cold-adapted bacteria survive in extremely cold temperature conditions and exhibit various mechanisms of adaptation to sustain their regular metabolic functions. These adaptations include several physiological and metabolic changes that assist growth in a myriad of ways. Successfully sensing of the drop in temperature in these bacteria is followed by responses which include changes in the outer cell membrane to changes in the central nucleoid of the cell. Their survival is facilitated through many ways such as synthesis of cryoprotectants, cold acclimation proteins, cold shock proteins, RNA degradosomes, Antifreeze proteins and ice nucleators. Agricultural productivity in cereals and legumes under low temperature is influenced by several cold adopted bacteria including Pseudomonas, Acinetobacter, Burkholderia, Exiguobacterium, Pantoea, Rahnella, Rhodococcus and Serratia. They use plant growth promotion mechanisms including production of IAA, HCN, and ACC deaminase, phosphate solublization and biocontrol against plant pathogens such as Alternaria, Fusarium, Sclerotium, Rhizoctonia and Pythium.

Micronutrients (Zn/Mn), seaweed extracts, and plant growth-promoting bacteria as cold-stress protectants in maize

“…This study was designed to compare the efficiency of different mitigation strategies against low root zone temperatures during early growth as a major constraint for maize cultivation in temperate climates [1][2][3][4], including supplementation of critical micronutrients (Zn, Mn) [14], application of seaweed extracts [15], and inoculation with plant growth-promoting and cold-tolerant bacteria [16]. Surprisingly, despite a proven plant growth-promoting potential [24,25] even in combination with the tested maize cultivar [26,27], the investigated microbial inoculants, including a psychrotolerant strain of Bacillus simplex, failed to show any beneficial effects on growth of maize seedlings exposed to moderately low RZT of 12-14 °C.…”

“…Surprisingly, despite a proven plant growth-promoting potential [24,25] even in combination with the tested maize cultivar [26,27], the investigated microbial inoculants, including a psychrotolerant strain of Bacillus simplex, failed to show any beneficial effects on growth of maize seedlings exposed to moderately low RZT of 12-14 °C. It remains to be established whether other cold-resistant microbial inoculants, directly isolated from the maize rhizosphere, such as Acinetobacter rhizosphaerae BIHB727, Pseudomonas putida B0, or Mycoplana bullata MpB46 [16], could be more effective in this context. In accordance with the observations of Imran et al [14], supplementation of critical micronutrients, particularly Zn, was effective in mitigating growth depressions (Fig.…”

“…The various successful application modes and formulations, such as seed priming, seed dressing, fertigation, supplementation in form of pure mineral nutrients or as seaweed extracts may offer high flexibility for different sowing techniques, underfoot fertilization, organic vs conventional farming etc., but still requires optimization of the application dosage. Apart from improved cold-stress tolerance, both, micronutrient fertilization and seaweed extracts have documented effects on plant growth promotion and tolerance against other biotic and abiotic stress factors [16,17,34]. Therefore, additional beneficial effects may be expected under stress conditions not addressed in the present study.…”

“…Improving root growth and plant nutrient acquisition by inoculation with plant growth-promoting microorganisms (PGPRs), particularly using cold-tolerant bacterial strains (psychrotolerant bacteria) with the ability to maintain phytohormone production, nutrient mobilization (siderophores), or degradation of excessive ethylene levels even at low soil temperatures (reviewed by Subramanian et al [16]). …”

Draft genome of Kocuria polaris CMS 76orT isolated from cyanobacterial mats, McMurdo Dry Valley, Antarctica: an insight into CspA family of proteins from Kocuria polaris CMS 76orT

“…At the same time, the observation that cspG is absent in all the species except K. palustris does not imply any specific role with respect to temperature adaptation. Several years ago we had demonstrated that cspA is induced under cold stress and constitutively expressed in psychrotolerant bacteria (Ray et al 1994(Ray et al , 1998Chattopadhyay 2006;Subramanian et al 2011). It is also established that cspC is expressed constitutively under normal growth conditions at 37 °C (Yamanaka et al 1994(Yamanaka et al , 1998, discounting its involvement in cold adaptation.…”