Prospecting microbial biofilms as climate smart strategies for improving plant and soil health: A review

Microbes and their products play key roles in complementing chemical fertilizers and plant protection chemicals by eliciting defence mechanisms in crop plants,thereby providing immunity and resistance against diverse stresses.Among the different environmental technologies used to mitigate climate change,several microbiological interventions are promising,among which biofilms,both naturally-existing and laboratory-developed,and their application have gained momentum recently.Microbial biofilms are aggregations of microbial cells in a self-generated polymeric matrix,which are produced by several genera of bacteria,yeasts,cyanobacteria,and fungi as a mode of reproductive fitness,thereby advantageous in successful proliferation,even in extreme environments.The propensity of microbial biofilms to grow in diverse niches and adapt to biotic and abiotic stresses illustrates their immense potential as biofertilizers and disease suppression options in various crops across diverse ecologies.In the inhospitable habitats of deserts and denudated land,biofilms play an important role in preventing soil erosion and sustaining vegetation,microflora,and fauna.Biofilms represent a mode of growth for several microbes with plant growth-promoting and biocontrol potential,which are important in seed establishment and the facilitation of exchanging nutrients and metabolites from the environment.In this review,we discuss the prospects of microbial biofilms as a green option in agriculture in general and,more specifically,their potential in mitigating climate change.

Chrysanthemum Growth Gains from Beneficial Microbial Interactions and Fertility Improvements in Soil Under Protected Cultivation

An investigation was undertaken to analyse the influence of microbial inoculants on growth and enzyme activities elicited, and soil microbiome of two varieties of Chrysanthemum morifolium Ramat, which were grown under protected mode of cultivation. Rhizosphere soil sampling at 45 and 90 DAT(days after transplanting of cuttings) revealed up to four- to five-fold enhancement in the activity of defence-, and pathogenesisrelated, and antioxidant enzymes, relative to the uninoculated control. Plant growth and soil microbial parameters, especially soil microbial biomass carbon and potential nitrification exhibited significant increases over control. Available soil nitrogen concentrations showed 40%–44% increment in inoculated treatments. Scanning electron microscopy of the root tissues revealed biofilm-like aggregates and individual short bits of cyanobacterial filaments. Analyses of DGGE profiles of archaeal and bacterial communities did not show temporal variations(between 45 and 90 DAT). However,distinct influences on the number and abundance of phylotypes due to microbial inoculants were recorded. The inoculants — Cyanobacterial consortium(BF1- 4) and Anabaena sp.–Trichoderma sp. biofilm(An-Tr) were particularly promising in terms of the plant and soil related parameters,and remained distinct in the DGGE profiles generated. The effect of Trichoderma viride–Azotobacter biofilm on soil bacterial and archaeal communities was unique and distinct as a separate cluster. This study highlights that microbial inoculants exert positive effects, which are specific even to the rhizosphere soil microbiome of chrysanthemum varieties tested. Such inoculants can serve as soil fertility enhancing options in protected floriculture.