Harnessing the Power of Traditional Organic Formulations for Crop Growth and Microbial Harmony.

The utilization of various agrochemicals in crop production technology leads to soil health and fertility depletion. Multiple measures have been taken to revitalize the health of polluted soil. In this context, organic agriculture has increased over the past few years to overcome the detrimental effects of extensive modern agricultural practices. Several traditional organic formulations, such as panchagavya, jeevamurtha, beejamurtha, bokashi, etc., are vital in converting polluted farmlands into organic. Various countries have their own organic formulations to improve crop growth and yield. These formulations are rich sources of many macro and micronutrients, growth-promoting phytohormones, and provide resistance against biotic and abiotic stresses. Apart from these benefits, these formulations consist of several groups of beneficial microorganisms that belong to the phyla Proteobacteria, Firmicutes, Bacteroides, and Actinobacteria, while some of the novel groups of microorganisms were also reported from the ingredients used in the preparation of these organic formulations. These microorganisms can solubilize nutrients such as phosphorous and zinc, oxidize sulfur, reduce nitrate, and are also involved in the production of indole acetic acid, ethylene reduction enzyme (1-aminocyclopropane-1-carboxylic acid deaminase), and organic acids that promote plant growth and induce resistance in the plant system. Hence, the utilization of traditional organic formulations helps in the reclamation of environmental health without compromising crop yields. This review describes the importance of organic farming, the preparation and application of different types of traditional organic formulations in different countries, and the microbial composition and mechanism of growth promotion of different traditional organic formulations.

Gamma-induced mutants of Bacillus and Streptomyces display enhanced antagonistic activities and suppression of the root rot and wilt diseases in pulses.

This study aims to increase Bacillus and Streptomyces antagonistic activity against the root rot and wilt diseases of pulses caused by Macrophomina phaseolina and Fusarium oxysporum f. sp. udum, respectively. To increase antagonistic action, Bacillus subtilis BRBac4, Bacillus siamensis BRBac21, and Streptomyces cavourensis BRAcB10 were subjected to random mutagenesis using varying doses of gamma irradiation (0.5-3.0 kGy). Following the irradiation, 250 bacterial colonies were chosen at random for each antagonistic strain and their effects against pathogens were evaluated in a plate assay. The ERIC, BOX, and random amplified polymorphic studies demonstrated a clear distinction between mutant and wild-type strains. When mutants were compared to wild-type strains, they showed improved plant growth-promoting characteristics and hydrolytic enzyme activity. The disease suppression potential of the selected mutants, B. subtilis BRBac4-M6, B. siamensisi BRBac21-M10, and S. cavourensis BRAcB10-M2, was tested in green gram, black gram, and red gram. The combined inoculation of B. siamensis BRBac21-M10 and S. cavourensis BRAcB10-M2 reduced the incidence of root rot and wilt disease. The same treatment also increased the activity of the defensive enzymes peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase. These findings suggested that gamma-induced mutation can be exploited effectively to improve the biocontrol characteristics of Bacillus and Streptomyces. Following the field testing, a combined bio-formulation of these two bacteria may be utilised to address wilt and root-rot pathogens in pulses.

Gallic Acid an Agricultural Byproduct Modulates the Biofilm Matrix Exopolysaccharides of the Phytopathogen Ralstonia solanacearum.

Ralstonia solanacearum is a soil-borne plant pathogen which causes wilt disease in economically important crops of the Solanaceae family in tropical and temperate regions. As biofilm formation is the major virulence factor in R. solanacearum, research inputs are necessary to identify natural biofilm inhibitors to mitigate virulence of this bacterium. Hence in the present work, the anti-biofilm potential of phytochemical compound gallic acid (GA) isolated from an agricultural byproduct (cashewnut shell) was investigated. Initially the Minimum inhibitory concentration (MIC) of crude extracts of cashewnut shell and coconut shell against R. solanacearum were investigated. The MIC of both the extracts were 400 µg/ml and their sub-MIC (200 µg/ml) inhibited biofilms in the range of 62-70% and 49-57%, respectively. As the cashewnut shell extract have higher biofilm inhibitory effect compared to coconut shell extract, we proceeded our further study by isolating the major compound GA from cashewnut shell by acid hydrolysate method. The sub-MIC of crude cashewnut shell extract inhibited 85% of young biofilms. The MIC of GA were observed at 3 mg/ml and sub-MIC (1.5 mg/ml) was found to eradicate 85% of mature biofilms which was confirmed by standard crystal violet assay and the biofilm reduction was further visualized under light microscopy and scanning electron microscopic images. Toxicity of GA was evaluated against R. solanacearum through XTT cell viability assay and found no antibacterial effect at sub-MIC. Additionally, it is confirmed with growth curve and time kill assays. Swimming and twitching motility were considered as an important virulence factors to invade plants and to block the xylem vessels. Therefore, sub-MIC of GA was found to inhibit both swimming and twitching motility of about 93% and 63% respectively. Anti-biofilm efficacy of GA was also worked well with tomato plant model where remarkable biofilm inhibition was found on treatment with GA before and after 24 h of infection with R. solanacearum. Hence GA will be an alternative, cheap source which is eco-friendly as well as novel source for the treatment of R. solanacearum biofilms and to prevent wilt disease in important crops.

Endomicrobial Community Profiles of Two Different Mealybugs: Paracoccus marginatus and Ferrisia virgata.

Mealybugs (Hemiptera: Coccomorpha: Pseudococcidae) harbour diverse microbial symbionts that play essential roles in host physiology, ecology, and evolution. In this study we aimed to reveal microbial communities associated with two different mealybugs, papaya mealybug (Paracoccus marginatus) and two-tailed mealybug (Ferrisia virgata) collected from the same host plant. Comparative analysis of microbial communities associated with these mealybugs revealed differences that appear to stem from phylogenetic associations and different nutritional requirements. This first report on both bacterial and fungal communities associated with these mealybugs provides a preliminary insight on factors affecting the endomicrobial communities. .

Azospirillum ramasamyi sp. nov., a novel diazotrophic bacterium isolated from fermented bovine products.

A Gram-stain-negative, rod-shaped, aerobic bacterium, designated M2T2B2T, was isolated from fermented bovine products in Suwon, Republic of Korea. The strain displayed growth at 15-45 °C (optimum, 28-30 °C), pH 6.0-10.0 (pH 7.0) and 0-2 % (w/v) NaCl (0 %). Colonies were light pink-coloured, round and convex. The cells were positive for oxidase and weakly positive for catalase. The major fatty acids in whole cells of strain M2T2B2T were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), followed by summed feature 3 (C16 : 1ω7c/C16 : 1ω6c), summed feature 2 (C12 : 0 aldehyde/unidentified 10.928/C14 : 0 3-OH/iso-C16 : 1 I), C16 : 0, C18 : 1 2-OH, C16 : 0 3-OH and C17 : 1ω6c. The polar lipids were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylcholine, phosphatidylglycerol, and three unidentified aminolipids. Ubiquinone 10 was the predominant ubiquinone. The DNA G+C content was 68.0 mol%. The strain could fix atmospheric nitrogen, which was evaluated by the acetylene reduction assay. Further, whole genome sequence analysis revealed the presence of a nif gene cluster. Strain M2T2B2T showed the highest 16S rRNA, rpoD and nifH gene sequence similarity to members of the genus Azospirillum, and showed 97.6 % 16S rRNA gene sequence similarity to Azospirillum oryzae COC8T. The phenotypic, phylogenetic and genomic analyses support the proposal of strain M2T2B2T as being a novel species of the genus Azospirillum, for which the name Azospirillumramasamyi sp. nov. is proposed. The type strain is M2T2B2T (=KACC 14063T=NBRC 106460T).

Arachidicoccus rhizosphaerae gen. nov., sp. nov., a plant-growth-promoting bacterium in the family Chitinophagaceae isolated from rhizosphere soil.

Three novel bacterial strains, designated Vu-144(T), Vu-7 and Vu-35, were isolated on minimal medium from rhizosphere soil of field-grown cowpea and subjected to a taxonomic study using a polyphasic approach. Cells of the strains were Gram-stain-negative, non-motile, non-spore-forming, coccoid rods, and formed non-pigmented colonies. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain Vu-144(T) was affiliated with an uncultivated lineage of the phylum Bacteroidetes. Its closest phylogenetic neighbour was the recently described species Niastella populi, a member of the family Chitinophagaceae, with just 90.7 % sequence similarity to the type strain. The only isoprenoid quinone detected was menaquinone 7 (MK-7). The fatty acid profiles showed large amounts of iso-C15 : 0, iso-C17 : 0 3-OH and iso-C15 : 1 G and minor amounts of summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH), C16 : 0 and other fatty acids, allowing the differentiation of the strains from other genera. The G+C content of the genomic DNA of the three strains ranged from 43.1 to 44.3 mol%. In addition to phosphatidylethanolamine, the major polar lipids were three unidentified aminophospholipids (APL1-APL3), two unidentified phospholipids (PL1, PL2) and three unidentified lipids (UL1-UL3). Biochemical test patterns also differed from those of Niastella populi and members of other genera. All three isolates showed plant-growth-promoting properties, e.g. the ability to produce indole-3-acetic acid and NH3 and to solubilize phosphate, utilized 1-aminocyclopropane 1-carboxylate (ACC) as a sole source of nitrogen and possessed the ACC deaminase enzyme. The novel isolates readily colonized roots and stimulated growth of tomato and cowpea under glasshouse conditions. Inoculated plants showed a 45-60 % increase in dry matter weight with respect to uninoculated controls. On the basis of the evidence from our polyphasic study, isolate Vu-144(T) represents a novel genus and species in the family Chitinophagaceae, for which the name Arachidicoccus rhizosphaerae gen. nov., sp. nov. is proposed. The type strain of Arachidicoccus rhizosphaerae is Vu-144(T) ( = KCTC 22378(T) = NCIMB 14473(T)).

Methylobacterium gossipiicola sp. nov., a pink-pigmented, facultatively methylotrophic bacterium isolated from the cotton phyllosphere.

A pink, aerobic, facultatively methylotrophic, motile, Gram-negative rod, designated Gh-105(T), was isolated from the phyllosphere of cotton from Coimbatore (Tamilnadu, India). 16S rRNA gene sequence analysis showed clearly that the isolate belonged to the Methylobacterium cluster. Strain Gh-105(T) was most closely related to Methylobacterium adhaesivum AR27(T) (99% 16S rRNA gene sequence similarity) and Methylobacterium iners 5317S-33(T) (97.5%). The isolate grew with C(1) compounds such as methanol and dichloromethane, but not with formaldehyde, formate, methylamine, trimethylamine or methane, as sole carbon sources and carried mxaF, which encodes methanol dehydrogenase and supports methylotrophic metabolism. The major fatty acid was C(18:1)ω7c and the G+C content of the genomic DNA was 64.2 mol%. Physiological and biochemical data and DNA-DNA relatedness with M. adhaesivum KACC 12195(T) and M. iners KACC 11765(T) revealed clear phenotypic and genotypic differences. For this reason, we propose that strain Gh-105(T) (=CCM 7572(T) =NRRL B-51692(T)) represents the type strain of a novel species, with the name Methylobacterium gossipiicola sp. nov.

Mucilaginibacter gossypii sp. nov. and Mucilaginibacter gossypiicola sp. nov., plant-growth-promoting bacteria isolated from cotton rhizosphere soils.

Two isolates from rhizosphere soil of cotton, designated Gh-67(T) and Gh-48(T), which produced large amounts of extracellular polysaccharide and possessed plant-growth-promoting traits, were characterized phenotypically and genotypically. The strains were Gram-negative and cells were non-motile rods that grew optimally at 28°C and grew between pH 4 and 7. 16S rRNA gene sequence analysis of strains Gh-67(T) and Gh-48(T) placed them in the genus Mucilaginibacter, with pairwise sequence similarity between them and type strains from related genera ranging from 93.9 to 98.2 %. The major fatty acids were iso-C15:0, C16:0 and summed feature 3 (C16:1ω7c and/or iso-C15:0 2-OH). The strains contained MK-7 as the major isoprenoid quinone. The DNA G+C contents of strains Gh-67(T) and Gh-48(T) were 46.7 and 44.2 mol%, respectively. The low DNA-DNA hybridization value (18 %) and a number of phenotypic differences between strains Gh-48(T) and Gh-67(T) indicated that they represent two separate species. Results of phenotypic, phylogenetic and genotypic analysis revealed that the strains were separated from the species of Mucilaginibacter described to date. Therefore, strains Gh-67(T) and Gh-48(T) represent novel species of Mucilaginibacter, for which we propose the names Mucilaginibacter gossypii sp. nov. (type strain Gh-67(T) =NCIMB 14470(T) =KCTC 22380(T)) and Mucilaginibacter gossypiicola sp. nov. (type strain Gh-48(T) =NCIMB 14471(T) =KCTC 22379(T)).

Leifsonia soli sp. nov., a yellow-pigmented actinobacterium isolated from teak rhizosphere soil.

Two yellow-pigmented, Gram-stain-positive, aerobic, motile, short rod-shaped bacteria were isolated from natural teak tree rhizosphere soil and their taxonomic positions were determined by using a polyphasic approach. Comparative 16S rRNA gene sequence analysis showed that strains TG-S248(T) and TG-S240 formed a distinct phyletic line within the genus Leifsonia. 16S rRNA gene sequence analysis of strain TG-S248(T) with sequences from Leifsonia shinshuensis DB 102(T), L. poae VKM Ac-1401(T), L. naganoensis DB 103(T), L. aquatica DSM 20146(T) and L. xyli subsp. cynodontis JCM 9733(T) revealed pairwise similarities ranging from 98.7 to 99.1 %. The major fatty acids were anteiso-C(15 : 0), anteiso-C(17 : 0) and iso-C(16 : 0). The G+C content of the DNA of the type strain was 69.4 mol%. DNA-DNA hybridization experiments revealed low levels of DNA-DNA relatedness (32 % or less) between strain TG-S248(T) and its closest relatives. Based on differences in phenotypic and genotypic characteristics, strain TG-S248(T) (=LMG 24767(T) =JCM 15679(T)) is designated the type strain of a novel species of the genus Leifsonia, for which the name Leifsonia soli sp. nov. is proposed.