Research Topic: Functional Genomic Analysis of Biofilm Determinants and Comparative Plasmid Genomics in Edwardsiella tarda GT163
Abstract: ** Lecture will be given in English** (249 words)
Rapid spread of antibiotic resistance genes (ARGs) in the environment poses critical threats to global public health. The overuse of antibiotics in aquaculture, such as bullfrog farms in Shantou, China, can lead to emergence and dissemination of multidrug-resistant (MDR) bacteria in the environment. Conjugation is a key mechanism that drives the spread of ARGs in bacteria populations. Previous studies have also shown that biofilms can provide favorable environment for conjugation among bacteria populations.
Edwardsiella tarda strain GT163, isolated from the frog farm sediments, is an MDR bacteria that exhibits a strong biofilm-forming phenotype. Genome-wide transposon (Tn) insertion mutagenesis revealed four key genes (nlpD, wecA, papB, and ptsI) distributed across the chromosome and plasmid that were essential for biofilm formation in E. tarda GT163. One plasmid (pGT163) from this bacterium is also predicted to be conjugative. Light and scanning electron microcopy approaches revealed a filamentous morphology in nlpD::Tn mutants. Interestingly, a mutation in the plasmid-born fimbrial pap gene cluster in the pGT163 suggests that biofilm phenotype can be disseminated by bacteria conjugation. Comparative analysis of 385 Edwardsiella plasmids from the NCBI database retrieved 58 plasmids that shared the incFIIrepA and 22 tra/trb-associated T4SS cluster. These plasmids were classified as PTU1 group with three distinct sub-lineages: PTU1-1, PTU1-2, and PTU1-3. The pGT163 belonged to the PTU1-3 subgroup.
This study defines critical genetic determinants of biofilm formation in E. tarda and provides a universal classification framework for Edwardsiella plasmids that harbor these important genes. These findings have broader implications for understanding biofilm formation in MDR Edwardsiella in aquaculture environments and the evolution of related plasmid lineages.
