Abstract
beta-lactamase has been well studied as an enzyme responsible for microbial surviving against various antibiotics and the spreading of the resistance. It could be existed in different microbes with 100% identity. Or, it could be existed in the same species as well as in different species in identities not equal to 100%. The question is, did the differences and the similarities between the beta-lactamase is due to mutations, host adaptation, its mobility, all of that or something else. This study aims to investigate different beta-lactamase belonging to one class (class C) to deep our understand to such differences. Our hypothesis is that beta-lactamases gain their differences due to both of mutation and host adaptation. The differences between thirty different beta-lactamases have been evaluated using different point of investigation including the protein and the DNA sequences and the beta-lactamases protein 3D structure models. The study suggests that host adaptation might be forced such kind of changes. And that changes might explain why different beta-lactamases existed in the same strain? That because of a second expected transformation from the recipient to the original host after such modification has been happened. This study is a single step toward the understanding of the confusing fact that beta-lactamase could be different within single strains and similar within different ones. As well as it, explain the global differences within the microbial strains. Our hypothesis might not absolutely correct but it should be considers as a material for further investigation and judgment.