Production, characterization and pesticidal potential of Bacillus species metabolites against sugar ant (Camponotus consobrinus)

In vitro and in vivo assessment of antimicrobial, enzymatic, and antifouling properties of self-potent lichen symbiotic bacteria

This study aimed to comprehensively assess the antimicrobial, antifouling, and antibiofilm-forming potential of lichen symbiotic bacteria against marine fouling bacterial strains. A total of 50 lichen-associated bacteria (LAB) isolates were successfully characterized and evaluated for their effectiveness in mitigating biofouling caused by various marine biofoulers. Through a battery of biological assays encompassing enzymatic, antagonistic, antimicrobial, and antifouling assays, 15 LAB isolates were identified based on their antagonist activities. Notably, the strain LAB4 exhibited remarkable performance across all bioassays, demonstrating its proficiency as an antifouling agent. The production of crude LAB extracts was successfully scaled up using a large-scale fermentor and further optimized. Additionally, a phylogenetic analysis of the isolated strain Bacillus proteolyticus D65's 16S ribosomal RNA gene revealed a high query coverage and percentage identity of 92.62% (accession no. MK883171.1). In conclusion, the lichen bacterial symbiotic isolate B. proteolyticus exhibited significant in vitro and in vivo inhibition of foulants. This study highlights the potential of lichens as a valuable source of yet unexplored bacteria. The bacterial consortium associated with Parmotrema sp. holds promise in combatting biofouling, which poses a substantial threat to the maritime industries and their economic stability.

Rhizospheric Bacillus spp. Exhibit Miticidal Efficacy against Oligonychus coffeae (Acari: Tetranychidae) of Tea

Oligonychus coffeae (Acari: Tetranychidae), popularly known as red spider mite (RSM) is one of the major pests of commercial tea (Camellia sinensis (L.) O. Kuntze) plantation world over. Many attempts have been made in the past to control this devastating pest using a variety of microbial bioagents, however, area-wise field success is very limited. We carried out an in vitro study to explore the potential of rhizospheric Bacillus spp. (B. amyloliquefaciens BAC1, B. subtilis LB22, and B. velezensis AB22) against O. coffeae through adulticidal and ovicidal activity. The 100% adult and egg mortality was observed with bacterial suspension (1 × 109 CFU/mL) by B. velezensis AB22, showing the lowest LC50 values for both adults and eggs of O. coffeae, i.e., 0.28 × 105 and 0.29 × 105, respectively. The study also throws some insights into the underlying mechanism through electron microscopy study and identification of some putative pesticidal metabolites from all the species. The three Bacillus species were observed to have four commonly secreted putative bioactive secondary metabolites, brevianamide A, heptadecanoic acid, thiolutin, and versimide responsible for their bio-efficacy against O. coffeae. The outcome of our study provides a strong possibility of introducing Bacillus spp. as a biological miticide and developing synthetic metabolites mimicking the mechanistic pathway involved in microbial bioefficacy.

The Antibacterial, Antitumor Activities, and Bioactive Constituents’ Identification of Alectra sessiliflora Bacterial Endophytes

Due to increased antimicrobial resistance against current drugs, new alternatives are sought. Endophytic bacteria associated with medicinal plants are recognized as valuable sources of novel secondary metabolites possessing antimicrobial, antitumor, insecticidal, and antiviral activities. In this study, five bacterial endophytes were isolated and identified from the medicinal plant, Alectra sessiliflora, and their antibacterial and antitumor activities were investigated. In addition, the crude extracts of the endophytes were analyzed using gas chromatography (GC) coupled with time-of-flight mass spectrometry (TOF-MS). The identified bacterial endophytes belong to three genera viz Lysinibacillus, Peribacillus, and Bacillus, with the latter as the dominant genus with three species. Ethyl acetate extracts from the endophytes were used for antimicrobial activity against eleven pathogenic strains through minimum inhibitory concentration (MIC). The antitumor activity against the Hela cervical, Hek 293 kidney, and A549 lung carcinoma cells was determined by the MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium] assay. Lysinibacillus sp. strain AS_1 exhibited broad antibacterial activity against the pathogenic strains with MIC values ranging from 4 to 8 mg/ml, while Bacillus sp. strain AS_3 displayed MIC of 0.25 mg/ml. Crude extracts of Lysinibacillus sp. strain AS_1, Peribacillus sp. strain AS_2, and Bacillus sp. strain AS_3 showed growth inhibition of more than 90% against all the cancer cell lines at a concentration of 1,000 μg/ml. Untargeted secondary metabolite profiling of the crude extracts revealed the presence of compounds with reported biological activity, such as antimicrobial, antioxidant, anti-inflammatory, antitumor, and antidiabetic properties. This study reported for the first time, bacterial endophytes associated with A. sessiliflora with antibacterial and antitumor activities.