Caulobacter endophyticus sp. nov., an endophytic bacterium harboring three lasso peptide biosynthetic gene clusters and producing indoleacetic acid isolated from maize root

Unlocking the potential of ecofriendly guardians for biological control of plant diseases, crop protection and production in sustainable agriculture

Several beneficial microbial strains inhibit the growth of different phytopathogens and commercialized worldwide as biocontrol agents (BCAs) for plant disease management. These BCAs employ different strategies for growth inhibition of pathogens, which includes production of antibiotics, siderophores, lytic enzymes, bacteriocins, hydrogen cyanide, volatile organic compounds, biosurfactants and induction of systemic resistance. The efficacy of antagonistic strains could be further improved through genetic engineering for better disease suppression in sustainable farming practices. Some antagonistic microbial strains also possess plant-growth-promoting activities and their inoculation improved plant growth in addition to disease suppression. This review discusses the characterization of antagonistic microbes and their antimicrobial metabolites, and the application of these BCAs for disease control. The present review also provides a comprehensive summary of the genetic organization and regulation of the biosynthesis of different antimicrobial metabolites in antagonistic strains. Use of molecular engineering to improve production of metabolites in BCAs and their efficacy in disease control is also discussed. The application of these biopesticides will reduce use of conventional pesticides in disease control and help in achieving sustainable and eco-friendly agricultural systems.

Limnobacter olei sp. nov., a Novel Diesel-Degrading Bacterium Isolated from Oil-Contaminated Soil

A bacterial strain P1T, capable of degrading diesel and converting thiosulfate to sulfate was isolated from an oil-contaminated soil sample. The cells were Gram-stain-negative, slightly curved rods and motile with a single polar flagellum. Growth of the strain was observed at 4-45 °C (optimum at 28 °C), at pH 4.0-12.0 (optimum at pH 10.0) and with 0-15.0% (w/v) NaCl (optimum at 2.0%). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain P1T was closely related to the members of the genus Limnobacter, with the highest sequence similarity to Limnobacter thiooxidans DSM 13612 T (99.8%), followed by Limnobacter alexandrii LZ-4 T (99.4%), Limnobacter parvus YS8-69 T (98.8%), Limnobacter litoralis KP1-19 T (97.6%), and Limnobacter humi UCM-39 T (97.5%). The draft genome sequence of strain P1T was 3.40 Mb long, with a DNA G + C content of 52.4%. The average nucleotide identity and digital DNA-DNA hybridization values between strain P1T and the closely related type strains were in the range of 71.8-85.1% and 18.1-28.7%, respectively. The predominant cellular fatty acids of strain P1T included C16: 0, summed feature 3 (C16: 1 ɷ7c and/or C16: 1 ɷ6c), summed feature 8 (C18: 1 ɷ7c and/or C18: 1 ɷ6c), and summed feature 7 (C19: 1 ɷ6c and/or C19: 1 ɷ7c and/or C19: 1 cyclo). In addition, the main polar lipid was composed of diphosphatidylglycerol, phosphatidylethanolamine, and phosphatidylglycerol. Q-8 was the sole respiratory quinone. Based on the polyphasic characterization, strain P1T (= KCTC 72814 T = CCTCC AB 2019403 T) represents a novel species of the genus Limnobacter, for which the name Limnobacter olei sp. nov. is proposed.

Bioprospecting and Challenges of Plant Microbiome Research for Sustainable Agriculture, a Review on Soybean Endophytic Bacteria

This review evaluates oilseed crop soybean endophytic bacteria, their prospects, and challenges for sustainable agriculture. Soybean is one of the most important oilseed crops with about 20-25% protein content and 20% edible oil production. The ability of soybean root-associated microbes to restore soil nutrients enhances crop yield. Naturally, the soybean root endosphere harbors root nodule bacteria, and endophytic bacteria, which help increase the nitrogen pool and reclamation of another nutrient loss in the soil for plant nutrition. Endophytic bacteria can sustain plant growth and health by exhibiting antibiosis against phytopathogens, production of enzymes, phytohormone biosynthesis, organic acids, and secondary metabolite secretions. Considerable effort in the agricultural industry is focused on multifunctional concepts and bioprospecting on the use of bioinput from endophytic microbes to ensure a stable ecosystem. Bioprospecting in the case of this review is a systemic overview of the biorational approach to harness beneficial plant-associated microbes to ensure food security in the future. Progress in this endeavor is limited by available techniques. The use of molecular techniques in unraveling the functions of soybean endophytic bacteria can explore their use in integrated organic farming. Our review brings to light the endophytic microbial dynamics of soybeans and current status of plant microbiome research for sustainable agriculture.