ABSTRACT
Antimicrobial resistance is a phenomenon that the present-day world is witnessing that poses a serious threat to global health. The decline in the development of novel therapeutics over the last couple of decades has exacerbated the situation further. In this scenario, the pursuit of new alternative therapeutics to commonly used antibiotics has gained predominance amongst researchers across the world. Antimicrobial peptides (AMPs) from natural sources have drawn significant interest in the recent years as promising pharmacological substitutes over the conventional antibiotics. The most notable advantage of AMPs is that microorganisms cannot develop resistance to them. Insects represent one of the potential sources of AMPs, which are synthesized as part of an innate immune defence against invading pathogens. AMPs from different insects have been extensively studied, and silkworm is one of them. Diverse classes of AMPs (including attacins, cecropins, defensins, enbocins, gloverins, lebocins and moricins) were identified from silkworm that exhibit antimicrobial property against bacteria, fungi and viruses, indicating their potential therapeutic benefits. This review briefs about the immune responses of silkworm to invading pathogens, the isolation of AMPs from silkworms, AMPs reported in silkworms and their activity against various microorganisms.
ABSTRACT
A Gram-staining-positive, solvent-tolerating (acetophenone, benzene, toluene, xylene and hexane), aerobic, non-motile, terminal endospore-forming, rod-shaped bacterium was isolated from a bottle of xylene. The strain, designated JC22(T), was found to be oxidase and catalase positive. The strain was able to tolerate solvents with different log p values like acetophenone (log P = 1.5), benzene (log P = 2.0), toluene (log P = 2.5), xylene (log P = 3.2) and hexane (log P = 3.4), though it could not use them as sole carbon sources. Based on the 16S rRNA gene sequence analysis, strain JC22(T) was identified as belonging to the genus Lysinibacillus and was most closely related to Lysinibacillus sinduriensis BLB-1(T) (98.1 %), Lysinibacillus halotolerans LAM612(T) (97.8 %), Lysinibacillus chungkukjangi 2RL3-2(T) (97.6 %) and Lysinibacillus xylanilyticus XDB9(T) (97.1 %). The DNA-DNA relatedness of strain JC22(T) with the type strains of closest species was <30 %. Strain JC22(T) grew chemoorganoheterotrophically with an optimal pH of 7-8 (range 6-10) at 35-37 °C (range 25-40 °C). The DNA G+C content was 41.2 mol%. The major cellular fatty acids were iso-C15:0, anteiso-C15:0 and iso-C16:0. Cell wall peptidoglycan type was determined to be A4α (L-Lys-D-Asp). Predominant quinone system was MK-7 with moderate amounts of MK-6, MK-6(H2) and MK-7(H2). Polar lipids of strain JC22(T) contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and an unidentified phospholipid. On the basis of morphological, physiological, genetic, phylogenetic and chemotaxonomical analyses, we conclude that strain JC22(T) be assigned the status of novel species of the genus Lysinibacillus for which the name Lysinibacillus xyleni sp. nov. is proposed. Type strain of the species is JC22(T) (= CCUG 57912(T) = KCTC 13604(T) = NBRC 105753(T) = DSM 23555(T)).
