# Phylogeny, Synteny, and Distribution of Type III Secretion Systems in Burkholderia cenocepacia: A Closer Look Into Host Span

## TL;DR

This study explores the distribution and evolution of T3SS genes in Burkholderia cenocepacia, revealing nine gene clusters and a unique SctF gene arrangement.

## Contribution

The study identifies nine T3SS gene clusters and a conserved orphan SctF gene in B. cenocepacia, offering new insights into T3SS evolution and host adaptation.

## Key findings

- Only one genome from a human clinical isolate lacked T3SS genes.
- Nine distinct T3SS gene clusters were identified, all lacking the sctF gene.
- A conserved orphan CDS encoding a putative SctF was found outside the T3SS clusters.

## Abstract

Type III secretion systems (T3SS) have been described in many Gram‐negative bacteria, including the human opportunistic pathogen Burkholderia cenocepacia, originally described in association with plants. The present work aimed to identify T3SS genes in a group of genomes of isolates from different sources, to gain insight into their role in the life cycle and host association of B. cenocepacia. Comparative and phylogenetic analyses were used to investigate the distribution, evolution, variability, and synteny of the T3SS genes within 48 genomes of B. cenocepacia. Only one genome, from a human clinical isolate, lacked T3SS genes. These results revealed 9 different clusters of T3SS genes within B. cenocepacia, all lacking an annotated needle protein gene (sctF) within the T3SS clusters. Interestingly, a CDS encoding a putative SctF was found outside the main T3SS gene clusters, which is highly conserved in all analyzed genomes. Taken together, these results suggest that the T3SS gene clusters seem to have been independently acquired and may play a pivotal role in pathogenicity, host range determination, and niche adaptation.

T3SS is a dedicated machinery that mediates interactions between bacteria and eukaryotic cells, providing a functional interface in pathogenic or symbiotic associations. Phylogenetic analyses and T3SS‐gene synteny revealed nine gene clusters, with no needle protein gene (sctF). However, an orphan CDS encoding a putative SctF was found.