Abstract
Bacterial biofilms are involved in adaptation to complex environments and are responsible for persistent bacterial infections. Biofilm formation is a highly complex process during which multifarious genes work together regularly. In this study, we screened the EZ-Tn5 transposon mutant library to identify genes involved in biofilm formation of Aeromonas hydrophila. A total of 24 biofilm-associated genes were identified, the majority of which encoded proteins related to cell structure, transcription and translation, gene regulation, growth and metabolism. The mutant strain TM90, in which a gene encoding oligopeptidase F (pepF) was disturbed, showed significant upregulation of biofilm formation compared to the parental strain. The TM90 colony phenotype was smaller, more transparent, and splendent. The adhesive ability of TM90 to HEp-2 cells was significantly increased compared with the parental strain. Fifty percent lethal dose (LD50) determinations in zebrafish demonstrated that the enhanced-biofilm mutant TM90 was highly attenuated relative to the wild-type strain. In conclusion, the pepF gene is demonstrated for the first time to be a negative factor for biofilm formation and is involved in A. hydrophila pathogenicity.
Highlights
Aeromonas hydrophila is a well-known opportunistic pathogen that widely exists in various aquatic environments (Janda and Abbott, 2010)
As a powerful approach for functional gene analysis, DNA transposition has been performed in multifarious bacteria, including Listeria monocytogenes (Chang et al, 2012), Riemerella anatipestifer (Wang X. et al, 2014), Pseudomonas putida (Xia et al, 2015) and Salmonella typhimurium (Sahu et al, 2013), to ascertain genetic determinants
We identified 24 biofilm-associated genes based on a library of 1030 mutant colonies of A. hydrophila, among which 14 genes were shown to enhance biofilm formation and 10 were involved in reducing biofilm formation
Summary
Aeromonas hydrophila is a well-known opportunistic pathogen that widely exists in various aquatic environments (Janda and Abbott, 2010) It infects fish and other aquatic animals, resulting in huge economic losses in the aquaculture industry, and causes various diseases in humans, such as skin infections, gastroenteritis, and necrotizing fasciitis. The biofilm is considered part of the pathogenic activity of various bacteria (Parsek and Singh, 2003; Kishikawa et al, 2013). Due to the ability to attach to visceral organs and many different material surfaces, biofilms have become major causes of persistent infection and drug resistance (Sakimura et al, 2015)
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