Pseudomonas
Glycosyl transferases are enzymes that catalyze the synthesis reaction of glycans and therefore, these enzymes have considerable control over surface variability of bacteria and how they interact with the host organism. This protein is ubiquitous in vertebrate, but rare in bacteria. Analysis of species-specific GC content using parametric methods identified the organism, Pseudemonas, in the human gastronitestinal tract with a 210 amino acid long sequence coding for the gene, HMPREF1030_01090, an uncharacterized protein (7.137784156 standard deviations from the mean). DarkHorse matched this gene with family 2 glycosyl transferase from Bifidobacterium longum (LPI 0.432), Clostridium cellulolyticum (LPI 0.458), Methanobrevibacter smithii (LPI 0.086), Lactobacillus salivarius (LPI 0.43), Brachyspira hyodysenteriae (LPI 0.482), Bacteroides pledbeius (0.460), Francisella tularensis (LPI 0.440), and others. Most of these organisms are pathogenic species of gram-negative bacteria that can be found in the human intestine.
These results suggest that glycosyl transferase is a necessary protein for cellular function and growth of microflora in the human gut microbiome. The degree of horizontal transfer events can be assumed based on the immense spread of this protein throughout many unrelated, yet, similarly structured bacteria. Our results identifying horizontal gene transferring of glycosyl transferase supports the nonlinear evolutionary history of this enzyme family.
Sugars are important antigenic factors that tell the body if something foreign is present and needs to be killed. The best antigenic factors are those that are unique to bacteria and not native to the host, or self. By determining the structure of glycans, glycosyl transferase can help the host distinguish between commensal and pathogenic bacteria. For instance, the lipopolysaccharide (LPS) of gram-negative bacteria is a prominent source of antigenic factors. Therefore, any variation in the LPS will allow bacteria to evade host immune defenses, aid in host adaptation, virulence and persistence. The acquisition of new glycosyl transferase genes by horizontal gene transfer can provide bacteria with a mechanism to evade host immune response by varying the highly variable O antigen and LPS of Gram-negative bacteria. A capsular polysaccharide biosynthesis protein from Clostridium perfringens was also identified by DarkHorse algorithm (LPI 0.017). This protein is important for synthesis of the outermost layer of bacteria, the capsule, and is capable of performing similar protective functions as glycosyl transferase that provides a selective advantage for bacterial pathogenicity.
