Identity Gene Expression in Proteus mirabilis

Abstract

Swarming colonies of independent Proteus mirabilis isolates recognize each other as foreign and do not merge together, whereas apposing swarms of clonal isolates merge with each other. Swarms of mutants with deletions in the ids gene cluster do not merge with their parent. Thus, ids genes are involved in the ability of P. mirabilis to distinguish self from nonself. Here we have characterized expression of the ids genes. We show that idsABCDEF genes are transcribed as an operon, and we define the promoter region upstream of idsA by deletion analysis. Expression of the ids operon increased in late logarithmic and early stationary phases and appeared to be bistable. Approaching swarms of nonself populations led to increased ids expression and increased the abundance of ids-expressing cells in the bimodal population. This information on ids gene expression provides a foundation for further understanding the molecular details of self-nonself discrimination in P. mirabilis.The gammaproteobacterium Proteus mirabilis is a leading cause of recurrent urinary tract infections and displays some extraordinary behaviors (15). P. mirabilis undergoes a morphologically distinct developmental cycle during growth on surfaces (reviewed in references 8, 15, and 18). Upon contact with a surface, flagellated rod-shaped swimmer cells (1 to 2 m in length) differentiate into hyperflagellated, polynucleoid, elongated cells (10 to 80 m in length). Colonies can swarm across surfaces rapidly, and the elongated cells, called swarmer cells, do not divide during migration. Expression of many virulence genes appears to be linked to swarmer cell differentiation, and there is a distinction between genes expressed during liquid growth and those expressed during surface-associated growth (1,2,5,6,16,18). The migrating front of a swarm will periodically arrest movement; cells will dedifferentiate to short cells and consolidate through cell division. After another round of differentiation, swarmer cells will migrate forward once again. This behavior results in colonies with a bull's-eyelike pattern (reviewed in references 8 and 18).Of particular interest to us, a boundary will form between approaching swarms of different strains but not between two swarms of a single strain (Fig. 1A). The boundary formation demonstrates that P. mirabilis populations have an ability to distinguish self from nonself. We recently identified a gene cluster, idsABCDEF, involved in P. mirabilis self versus nonself recognition (10). Swarms of Ids mutants form a boundary with their parent. Two of the genes, idsD and idsE, encode functions for determining strain-specific identity. Of the remaining genes, idsB, idsC, and idsF are required for self versus nonself recognition but are not identity determinants. The idsA gene is not required for recognition, but it has been termed an ids gene because idsA is possibly cotranscribed with idsBCDEF. There is no available information on ids gene expression.Bacterial colonies can be considered either as populations of cells or as populat...

Kin discrimination between sympatric Bacillus subtilis isolates

“…In addition, nonkin bacteria competed with each other to colonize plant roots, whereas kin strains cocolonized the same root surface. Boundary formation has been previously studied in the soil bacterium Myxococcus xantus (10) and in the pathogen P. mirabilis (16)(17)(18)20). In M. xanthus, the phenomenon was associated with competitive incompatibility of strains (10).…”

“…This Gram-negative urinary tract pathogen exhibits merging of genetically identical swarms, whereas swarms composed of different strains form a visible boundary and do not merge (16)(17)(18)(19)(20). Swarm merging has not been strictly correlated with relatedness in P. mirabilis, however, due to the lack of a diverse set of strains.…”

Pathogenesis of Proteus mirabilis Infection

“…This operon was found to encode a single immunity protein, PefE, which was responsible for providing immunity from killing by the Pef effectors. However, strain HI4320 was also found to encode at least four other potential T6S effector operons that could use the T6S apparatus, including idsABCDEF (175, 212) and three additional operons (PMI0207-PMI0212, PMI1117-PMI1121, and PMI1332-PMI1324) (112, 119) (Fig. 19).…”

Proteus mirabilisand Urinary Tract Infections

“…Recent studies suggest that type VI-mediated secretion of toxic effector proteins is the main mechanism of Dienes line formation (149, 150). Type VI secretion systems (T6SS) comprise a method of protein export that generally requires cell-cell contact, whether between two bacteria or a bacterium and a eukaryotic host cell.…”