Insight of Genus Corynebacterium: Ascertaining the Role of Pathogenic and Non-pathogenic Species

Abstract

This review gathers recent information about genomic and transcriptomic studies in the Corynebacterium genus, exploring, for example, prediction of pathogenicity islands and stress response in different pathogenic and non-pathogenic species. In addition, is described several phylogeny studies to Corynebacterium, exploring since the identification of species until biological speciation in one species belonging to the genus Corynebacterium. Important concepts associated with virulence highlighting the role of Pld protein and Tox gene. The adhesion, characteristic of virulence factor, was described using the sortase mechanism that is associated to anchorage to the cell wall. In addition, survival inside the host cell and some diseases, were too addressed for pathogenic corynebacteria, while important biochemical pathways and biotechnological applications retain the focus of this review for non-pathogenic corynebacteria. Concluding, this review broadly explores characteristics in genus Corynebacterium showing to have strong relevance inside the medical, veterinary, and biotechnology field.

Keywords: Corynebacterium; bacterial biochemistry; bacterial genomics; biotechnology of microorganisms; pathogenesis related genes.

Figure 1

Scheme of cell division in Corynebacterium genus. An overview of cell division in Corynebacterium describing the main proteins involved. The FtsZ ring formation being regulated by clpX or shaped by sepF. The set of fts proteins associated with FtsZ (FtsQ, FtsK, FtsW, and FtsI) able to organize cell division, and finally the Par system that is described as important for chromosome segregation. In addition, a short scheme illustrating how the FtsW can help on the chromosome segregation.

Figure 2

Scheme detailing the bacterial reproduction process in macrophages. A—The formed phagolysosome increases pH value and thereby increases PLD expression. Curiously, the phagolysosome is not able to digest the bacteria due to the presence of mycolic acid on the surface of the bacteria, inhibiting exocytosis. B—The high amount of PLD is enough to destroy the phagolysosome membrane by lysis, exposing the bacteria to the cytoplasm, in which they are able to survive and reproduce.

Figure 3

The sortase mechanism in gram-positive bacteria. As shown above for C. diphtheriae, pilins are thought to be translocated upon the cytoplasmic membrane (Export) and hold within the secretory pathway by the cell wall sorting signal CWSS (Retention). These biomolecules (cysteine transpeptidases) join proteins conducting an appropriate sorting signal to strategically positioned amino groups on the cell surface.

Figure 4

Mechanism in which the bacterial DT invades the host cell membrane. The toxin enters through the membrane by endocytosis with the aid of fragment B. Fragment A is then actively exposed to the cytoplasm. In acidic endosomes, its translocation domain inserts into endosomal membranes and facilitates the transport of the catalytic domain (DTA) from endosomal lumen into the host cell cytosol. Here, DTA ADP-ribosylates elongation factor 2 inhibits protein synthesis and leads to cell death (Schnell et al., 2016).