Inactivation of the Major Hemolysin Gene Influences Expression of the Nonribosomal Peptide Synthetase Gene swrA in the Insect Pathogen Serratia sp. Strain SCBI

Abstract

Hemolysins are important virulence factors for many bacterial pathogens, including The role of the major hemolysin gene in the insect pathogen sp. strain SCBI was investigated using both forward and reverse-genetics approaches. Introduction of the major hemolysin gene into resulted in a gain of both virulence and hemolytic activity. Inactivation of this hemolysin in sp. SCBI resulted in a loss of hemolysis but did not attenuate insecticidal activity. Unexpectedly, inactivation of the hemolysin gene in sp. SCBI resulted in significantly increased motility and increased antimicrobial activity. Reverse transcription-quantitative PCR (qRT-PCR) analysis of mutants with a disrupted hemolysin gene showed a dramatic increase in mRNA levels of a nonribosomal peptide synthetase gene,, which produces the surfactant serrawettin W2. Mutation of the gene in sp. SCBI resulted in highly varied antibiotic activity, motility, virulence, and hemolysis phenotypes that were dependent on the site of disruption within this 17.75-kb gene. When introduced into , increases rates of motility and confers antimicrobial activity. While it is unclear how inactivation of the major hemolysin gene influences the expression of , these results suggest that plays an important role in motility and antimicrobial activity in sp. SCBI. The opportunistic Gram-negative bacteria of the genus are widespread in the environment and can cause human illness. A comparative genomics analysis between and a new species from South Africa, termed sp. strain SCBI, shows that these two organisms are closely related but differ in pathogenesis. kills nematodes, while sp. SCBI is not harmful and forms a beneficial association with them. This distinction presented the opportunity to investigate potential differences in regulation of common virulence mechanisms between these two species. With the emergence of antibiotic-resistant microorganisms, there is a widespread need to understand the regulation of pathogenesis. The significance of this study is the presentation of evidence for cross-pathway regulation of virulence factors and how the elimination of one mechanism may be compensated for by the upregulation of others.

Antimicrobial resistance determinants in silage

“…Additional species may join the silage from animals, soil, or water: Acinetobacter gyllenbergii 46 , Citrobacter freundii 47 , Enterobacter asburiae 48 , E. cloacae 49 , E. roggenkampii 50 , E. sichuanensis 51 , Enterococcus faecalis 52 , Klebsiella aerogenes 53 , K. oxytoca 54 , Kluyvera intermedia 55 , Lactococcus garvieae 56 , Latilactobacillus curvatus 57 , Leclercia adecarboxylata 58 , Lelliottia amnigena 59 , Limosilactobacillus reuteri 28 , Providencia rettgeri 60 , Pseudescherichia vulneris 61 , Pseudomonas oryzihabitans 62 , Rhodopseudomonas palustris 63 , Serratia sp. SCBI 64 , Staphylococcus aureus 46 , S. kloosii 65 , S. pseudoxylosus 66 , S. saprophyticus 46 , Enterococcus faecium 52 . However, it can be assumed that other species may be present as contaminants: Acinetobacter baumannii, A. dispersus, Bacillus subtilis, Enterobacter hormaechei, E. kobei, E. ludwigii, E. cancerogenus, Klebsiella grimontii, Lacticaseibacillus manihotivorans, Latilactobacillus sakei, Lactiplantibacillus argentoratensis, Leclercia sp.…”