Figure 2. Schematic representation of envelope transport systems in Ramlibacter tataouinensis TTB310.

In addition to general export pathway (Sec and Tat systems), the strain TTB310 genome encodes one type I secretion system potentially involved in secretion of a large protein, which is a putative adhesin (Rta_27720) as found in Pseudomonas fluorescens [76], and two type II secretion systems (T2SS) potentially involved in secretion of putative hydrolase implicated in EPS remodelling. The T2SSs clusters (gspFGHIJKLMCDE or gspDHEFG), each encodes an ATPase (GspE), a secretin (GspD) and a major pseudopilin (GspG), though they contain only one copy of the gspAB genes. One type IV pili machinery with different pilins and three PilB paralogs is present in strain TTB310 and is potentially involved in gliding motility. There is only one gene (pilD/gspO) encoding a prepilin peptidase involved in the maturation of both type II secretion system and type IV pili machinery. The strain TTB310 type III secretion system (T3SS) may be an additional example of the presence of T3SS genes in a nonpathogenic bacterium [29]. It could be involved in the secretion of chitinases through the thick extracellular polymeric substances (EPS) of cyst-cells.