Isolation and characterisation of a new mosquitocidal bacterium strain ofEnterobacter cloacaeVCRC-B519 from marine soil

Abstract

A novel mosquitocidal bacterium was isolated from marine soil. 16S rRNA gene sequence alignment depicted that this isolate belonged to the strain, Enterobacter cloacae VCRC-B519 (NCBI: KC119193). Biochemical studies such as bacterial growth, biomass production and protein (toxin) synthesis showed that the strain is plausibly useful for mosquito control. It showed an increasing pattern of toxicity for Culex quinquefasciatus, Anopheles stephensi and Aedes aegypti, without negative effects for non-targeted organisms Chironomus riparius, Daphnia cephalata and Notonecta glauca. The qualitative analysis of the E. cloacae showed that three polypeptides (M.wt: 25, 30 and 50 kDa) were associated to the toxicity observed. The characterisation of these polypeptides (M/S MALDI-TOF)showed that they are enzymatic in nature. Consequently, the peptide sequences are identified to be polysugar degrading enzymes (25 kDa), cell wall associated hydrolases (30 kDa) and amino peptidase (50 kDa). Phylogenetic analyses of 16S rDNA gene sequence of E. cloacae revealed the occurrence of homology with closely related Enterobacter species. Therefore, it is concluded that the marine bacterium (Enterobacter cloacae)is possibly of use for the biological control of mosquito immatures.

Isolation of Mosquitocidal Bacteria from Soil Samples to Control Mosquito Vectors

“…Totally 140 soil samples were collected including red, clay loam, clay, sandy and loamy soil. These were screened for mosquitocidal bacteria, using serial dilution method (Poopathi et al, 2014;Hemaladkshmi et al, 2023). Bacterial colonies were isolated and cultured till 72 hr in NYSM broth.…”

“…One g of each soil sample was weighed and serially diluted (10 -3 ) (Poopathi et al, 2014). Using spread plate method 100 μl of the dilution was spread on nutrient yeast extract salt medium (NYSM) and incubated for 24 hr at room temperature.…”

Marine Natural Products: The Important Resource of Biological Insecticide

“…A novel cyclodepsipeptide named iso‐isariin D ( 58 ) together four known destruxin cyclodepsipeptides ( 59 – 62 ) were isolated from Beauveria felina EN‐135, a pathogenic fungus from a marine bryozoan and prominent in insecticidal activity tests [113] . Enterobacter cloacae VCRC−B519 obtained from marine soil was regarded as effective mosquitocidal bacterium, three peptides [114] isolated are thought to be related to the insecticidal activity of this bacteria. Study among marine soil collected from Pondicherry found a unique mosquitocidal bacterium and identified to be Bacillus cereus VCRC‐B520, isolation guided by its insecticidal activity discovered an insecticidal protein, namely “Cry4Aa”, [115] which can cause mosquito susceptibility of Culex quinquefasciatus.…”