Impact of Cell Surface Molecules on Conjugative Transfer of the Integrative and Conjugative Element ICE St3 of Streptococcus thermophilus

Abstract

Integrative conjugative elements (ICEs) are chromosomal elements that are widely distributed in bacterial genomes, hence contributing to genome plasticity, adaptation, and evolution of bacteria. Conjugation requires a contact between both the donor and the recipient cells and thus likely depends on the composition of the cell surface envelope. In this work, we investigated the impact of different cell surface molecules, including cell surface proteins, wall teichoic acids, lipoteichoic acids, and exopolysaccharides, on the transfer and acquisition of ICE from The transfer of ICE from wild-type (WT) donor cells to mutated recipient cells increased 5- to 400-fold when recipient cells were affected in lipoproteins, teichoic acids, or exopolysaccharides compared to when the recipient cells were WT. These mutants displayed an increased biofilm-forming ability compared to the WT, suggesting better cell interactions that could contribute to the increase of ICE acquisition. Microscopic observations of cell surface mutants showed different phenotypes (aggregation in particular) that can also have an impact on conjugation. In contrast, the same mutations did not have the same impact when the donor cells, instead of recipient cells, were mutated. In that case, the transfer frequency of ICE decreased compared to that with the WT. The same observation was made when both donor and recipient cells were mutated. The dominant effect of mutations in donor cells suggests that modifications of the cell envelope could impair the establishment or activity of the conjugation machinery required for DNA transport. ICEs contribute to horizontal gene transfer of adaptive traits (for example, virulence, antibiotic resistance, or biofilm formation) and play a considerable role in bacterial genome evolution, thus underlining the need of a better understanding of their conjugative mechanism of transfer. While most studies focus on the different functions encoded by ICEs, little is known about the effect of host factors on their conjugative transfer. Using ICE of as a model, we demonstrated the impact of lipoproteins, teichoic acids, and exopolysaccharides on ICE transfer and acquisition. This opens up new avenues to control gene transfer mediated by ICEs.

Chromosomal Conjugative and Mobilizable Elements in Streptococcus suis: Major Actors in the Spreading of Antimicrobial Resistance and Bacteriocin Synthesis Genes

“…Mating experiments were done as described in Dahmane et al [55]. Selection of transconjugants was made at 37 • C (for intraspecies S. suis mating), 39 • C (for interspecies from S. suis to S. thermophilus mating) or 42 • C (for intraspecies S. thermophilus mating) using tetracycline and chloramphenicol containing-LM17 plates.…”

“…Plasmid curing of the transconjugants used as donor cells in retro-transfer experiments was done as described previously [55].…”

Safety Aspects of Genetically Modified Lactic Acid Bacteria

“…Conjugation is the transfer of genetic material between bacterial cells by direct cell-to-cell transfer of DNA. Although conjugative plasmids and transposons are very common in LAB, the underlying mechanisms are not fully understood yet [10,16]. For phage transduction, the DNA transfer is mediated by bacteriophages, which are viruses that can infect bacteria and manipulate the bacterial replication, transcription, and translation machineries to drive their own proliferation.…”

Mobilization of IMEs Integrated in the oriT of ICEs Involves Their Own Relaxase Belonging to the Rep-Trans Family of Proteins

“…Overlap PCR was used to insert an antibiotic resistance gene in integrative elements of S. salivarius L25 as described previously [ 21 ]. Deletion of the integrase genes (of ICE SsalF1-4_fda in S. salivarius F1-4 and ICE St3 of S. thermophilus in LMG18311) was done by insertion of a chloramphenicol resistance cassette as described previously [ 24 ]. IME_ SsalL25_oriT and 1-kb-upstream and downstream flanking regions were PCR-amplified before natural transformation of S. thermophilus LMG18311(ICE St3 ) as described by Gardan et al [ 25 ].…”