Researchers have identified a unique enzyme in the opportunistic pathogen Clostridium perfringens that degrades hyaluronan, a critical component of the extracellular matrix in the human gut. This finding sheds light on how this bacterium can colonize and infect the intestinal tract. The study reveals that Clostridium uses a hyaluronate lyase, rather than the previously suspected hyaluronidases, to break down hyaluronan and potentially gain access to host tissues. This discovery has important implications for understanding the pathogenicity of Clostridium and could lead to new strategies for combating gut infections. The research provides a fascinating glimpse into the intricate interactions between bacteria and their human hosts. Clostridium perfringens, Hyaluronan, Extracellular matrix, Gut microbiome, Pathogenicity
Uncovering a Unique Enzyme in Clostridium perfringens
Clostridium perfringens is a formidable opportunistic pathogen that can cause life-threatening infections in humans, such as gas gangrene and food poisoning. This Gram-positive, anaerobic bacterium is a common inhabitant of the human gut, but its ability to thrive and cause disease remains a subject of intense research.
Hyaluronan, a key component of the extracellular matrix, is abundant in the gut epithelium and serves as a potential nutrient source for gut bacteria. The ability to degrade hyaluronan is considered a virulence factor for many pathogens, as it can facilitate tissue invasion and colonization. Previous studies had suggested that Clostridium perfringens utilizes hyaluronidases, known as mu-toxins, to degrade hyaluronan.
However, the current study by researchers from Kyoto University in Japan has uncovered a surprising finding: the intrinsic hyaluronan-degrading enzyme in Clostridium perfringens strain ATCC 13124 is not a hyaluronidase, but rather a hyaluronate lyase called CpeHysA.
Identifying the Hyaluronan-Degrading Enzyme
The researchers began by examining the ability of Clostridium perfringens and other related species to degrade various glycosaminoglycans (GAGs), including hyaluronan, chondroitin sulfate, and heparin. They found that Clostridium perfringens was the only species capable of degrading hyaluronan, as evidenced by the formation of a clear halo on agar plates.
Further analysis using RNA-sequencing (RNA-seq) revealed that in the presence of hyaluronan, Clostridium perfringens upregulated the expression of a gene cluster containing the hysA gene, which encodes the hyaluronate lyase CpeHysA. Interestingly, the expression of genes encoding the previously suspected hyaluronidases, such as nagH, nagJ, and nagK, was actually repressed under these conditions.
To confirm the role of CpeHysA, the researchers cloned and expressed the gene in Escherichia coli. The recombinant CpeHysA enzyme exhibited robust hyaluronan-degrading activity, producing unsaturated hyaluronan disaccharides as the primary products. Additionally, the hyaluronan-degrading activity in the culture supernatant of Clostridium perfringens was found to be identical to the recombinant CpeHysA, further validating its role as the intrinsic hyaluronan-degrading enzyme.
Structural Insights and Implications
Structural modeling of CpeHysA revealed that it is a member of the polysaccharide lyase family 8, similar to the well-studied hyaluronate lyase from Streptococcus pneumoniae. The model showed that CpeHysA contains the conserved catalytic residues essential for the β-elimination reaction, which cleaves the glycosidic bond of hyaluronan.
This discovery that Clostridium perfringens relies on a hyaluronate lyase, rather than hyaluronidases, for hyaluronan degradation is a significant finding. It suggests that the bacterium has evolved a unique mechanism to access and utilize this abundant gut component as a nutrient source. The upregulation of the GAG genetic cluster, which includes genes involved in the import, degradation, and metabolism of the unsaturated hyaluronan disaccharides, further supports this hypothesis.
Implications and Future Directions
The identification of CpeHysA as the intrinsic hyaluronan-degrading enzyme in Clostridium perfringens has important implications for understanding the pathogenicity of this opportunistic pathogen. Hyaluronan degradation is considered a virulence factor, as it can facilitate tissue invasion and colonization. This newfound knowledge could lead to the development of targeted therapies or preventive strategies to combat Clostridium infections.
Moreover, the study sheds light on the complex interactions between gut bacteria and their human hosts. The ability of Clostridium to degrade and utilize hyaluronan, a key component of the extracellular matrix, highlights the sophisticated mechanisms employed by these microorganisms to thrive in the gut environment. Further research into the regulation and function of the GAG genetic cluster may uncover additional insights into the metabolic adaptations and virulence strategies of Clostridium perfringens.
In conclusion, this study’s discovery of the hyaluronate lyase CpeHysA as the primary hyaluronan-degrading enzyme in Clostridium perfringens represents a significant advancement in our understanding of this opportunistic pathogen’s interactions with the human gut. The findings open up new avenues for exploring the role of hyaluronan in bacterial colonization and infection, potentially leading to the development of novel therapeutic approaches to combat Clostridium-related diseases.
Author credit: This article is based on research by Tomoya Kumon, Sayoko Oiki, Wataru Hashimoto.
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