Halomonas icarae sp. nov., a moderately halophilic bacterium isolated from beach soil in India.

A moderately halophilic, Gram-stain-negative, aerobic bacterium, strain D1-1T, belonging to the genus Halomonas, was isolated from soil sampled at Pentha beach, Odisha, India. Phylogenetic trees reconstructed based on 16S rRNA genes and multilocus sequence analysis of gyrB and rpoD genes revealed that strain D1-1T belonged to the genus Halomonas and was most closely related to Halomonas alimentaria YKJ-16T (98.1 %) followed by Halomonas ventosae Al12T (97.5 %), Halomonas sediminicola CPS11T (97.5 %), Halomonas fontilapidosi 5CRT (97.4 %) and Halomonas halodenitrificans DSM 735T (97.2 %) on the basis of 16S rRNA gene sequence similarity. Sequence identities with other species within the genus were lower than 97.0 %. The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values of 22.4-30 % and 79.5-85.4 % with close relatives of H. halodenitrificans DSM 735T, H. alimentaria YKJ-16T, H. ventosae Al12T and H. fontilapidosi 5CRT were lower than the threshold recommended for species delineation (70 % and 95-96 % for dDDH and ANI, respectively). Further, strain D1-1T formed yellow-coloured colonies; cells were rod-shaped, motile with optimum growth at 30 °C (range, 4-45 °C) and 2-8 % NaCl (w/v; grew up to 24 % NaCl). The major fatty acids were summed feature 8 (C18 : 1 ω7c/C18 : 1 ω6c), summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c) and C16 : 0 and the main respiratory quinone was ubiquinone Q-9 in line with description of the genus. Based on its chemotaxonomic and phylogenetic characteristics and genome uniqueness, strain D1-1T represents a novel species in the genus Halomonas, for which we propose the name Halomonas icarae sp. nov., within the family Halomonadaceae. The type strain is D1-1T (=JCM 33602T=KACC 21317T=NAIMCC-B-2254T).

Bacterial endophyte mediated plant tolerance to salinity: growth responses and mechanisms of action.

Salinity stress is one of the key constraints for sustainable crop production. It has gained immense importance in the backdrop of climate change induced imbalanced terrestrial water budgets. The traditional agronomic approaches and breeding salt-tolerant genotypes have often proved insufficient to alleviate salinity stress. Newer approaches like the use of bacterial endophytes associated with agricultural crops have occupied center place recently, owing to their advantageous role in improving crop growth, health and yield. Research evidences have revealed that bacterial endophytes can promote plant growth by accelerating availability of mineral nutrients, helping in production of phytohormones, siderophores, and enzymes, and also by activating systemic resistance against insect pest and pathogens in plants. These research developments have opened an innovative boulevard in agriculture for capitalizing bacterial endophytes, single species or consortium, to enhance plant salt tolerance capabilities, and ultimately lead to translational refinement of crop-production business under salty environments. This article reviews the latest research progress on the identification and functional characterization of salt tolerant endophytic bacteria and illustrates various mechanisms triggered by them for plant growth promotion under saline environment.

Sustainable use of the spent mushroom substrate of Pleurotus florida for production of lignocellulolytic enzymes.

Spent mushroom substrate (SMS), a major byproduct of the mushroom industry, is a lignocellulosic biomass, which contains approximately 57-74.3% of holocellulose fraction. This study was aimed at utilizing SMS of Pleurotus florida for recovery of lignocellulolytic enzymes and sugars and also as a substrate for production of cellulolytic enzymes using different isolates of Trichoderma and Aspergillus under solid-state fermentation (SSF). SMS of P. florida extracts contained significant amounts of laccase (3,015.8 ± 29.5 U/g SMS) and xylanase (1,187.9 ± 12 U/g SMS) activity. Crystallinity pattern and chemical changes in SMS revealed that SMS had a lower crystallinity index (34.2%) as compared with the raw biomass (37.8%), which, in turn, helps in enhancing the accessibility of cellulolytic enzymes to holocellulose. Among the isolates, Trichoderma longibrachiatum A-01 showed maximum activity of endoglucanase (220.4 ± 5.9 U/mg), exoglucanase (78.5 ± 3.2 U/mg) and xylanase (1,550.4 ± 11.6 U/mg) while Aspergillus aculeatus C-08 showed maximum activity of cellobiase (113.9 ± 3.9 U/mg). Extraction with sodium citrate buffer (pH 4.8) showed maximum cellulolytic enzyme activity as compared with other solvents tested. Partial purification of endoglucanase, exoglucanase, xylanase, and cellobiase resulted in 56.3% (1,112.5 U/mg), 48.4% (212.5 U/mg), 44% (4,492.3 U/mg), and 62% (705.0 U/mg) yield with an increase by 5.2-, 4.5-, 4.1-, and 5.0-fold as compared with crude extract. The results reveal that SMS from P. florida could be a potential and cost-effective substrate for production of cellulolytic enzymes from T. longibrachiatum A-01 and A. aculeatus C-08.

Plant growth promoting and antifungal activity in endophytic Bacillus strains from pearl millet (Pennisetum glaucum).

Bacterial endophytes are well known inhabitants of living plant system and perform important assignments in maintaining plant growth and health. Currently, limited reports are available on the endophytes of pearl millet (Pennisetum glaucum) reflecting antagonistic and plant growth promoting (PGP) attributes. Therefore, the major objectives of current investigation were to identify antagonistic strains of endophytic Bacillus from pearl millet and further illustrate their PGP capabilities. In this study, 19 endophytic Bacillus strains (EPP5, EPP21, EPP30, EPP32, EPP35, EPP42, EPP49, EPP55, EPP62, EPP65, EPP70, EPP71, EPP74, EPP78, EPP83, EPP86, EPP93, EPP100, and EPP102) displaying antagonistic activity towards Rhizoctonia solani (RS), Sclerotium rolfsii (SR), and Fusarium solani (FS) were isolated from different sections (root, leaf, stem, and root) of pearl millet. Phenotypic (shape, colony, gram staining reaction, endospore formation, and motility) and biochemical features (catalase, oxidase, citrate, gelatinase, urease, Voges Proskauer's, methyl red, indole, and nitrate reduction), along with the similarly comparison of 16S rRNA gene sequence with type strains identified eight antagonistic endophyhtes as B. amyloliquefaciens (EPP35, EPP 42, EPP62, and EPP 102), Bacillus subtilis subsp. subtilis (EPP65), and Bacillus cereus (EPP5, EPP71, and EPP74). The production of indole acetic acid and siderophores was varied among the isolated endophytes. Besides displaying enzymatic activities, these isolates varied in solubilizing capabilities of phosphate, potassium, and zinc. The presence of three antimicrobial peptide genes (ituD, bmyC, and srfA) also confirmed their antifungal nature. Further, single treatment of three promising strains (EPP5, EPP62, and EPP65) offered protection ranging from 35.68 to 45.74% under greenhouse conditions. However, microbial consortium (EPP5+ EPP62 + EPP65) provided the highest protection (71.96%) against root rot and wilt infection with significant increase in plant biomass. Overall, the current study indicated that pearl millet plant harbors various species of endophytic Bacillus that possess excellent biocontrol and growth promotion activities.