Mercuric resistance genes in gram-positive oral bacteria

Area of Science:

• Microbiology
• Genetics
• Environmental Health

Background:

• Mercury resistance is a significant environmental and health concern.
• The merA gene is crucial for mercury detoxification in bacteria.
• Oral bacteria are increasingly recognized as reservoirs for antibiotic and heavy metal resistance genes.

Purpose of the Study:

• To investigate the diversity and genetic context of merA genes in oral bacteria from children.
• To understand the evolutionary origins and mechanisms of mercury resistance in the oral microbiome.
• To identify novel genetic elements associated with merA genes in oral bacteria.

Main Methods:

• Bacterial isolation from oral cavities of children.
• Molecular identification of merA gene types using PCR and sequencing.
• Comparative genomic analysis to determine the genetic environment of merA genes.
• Phylogenetic analysis to infer evolutionary relationships.

Main Results:

• Two distinct types of merA genes were identified in oral bacteria.
• One merA type, found in Streptococcus species, showed high similarity to Bacillus cereus merA but was located on a novel type II transposon, not Tn5084-like transposons.
• Coagulase-negative staphylococci and Streptococcus parasanguis harbored identical merA genes, representing a new variant.

Conclusions:

• Oral bacteria in children harbor diverse merA genes, suggesting horizontal gene transfer and adaptation.
• The identification of a novel type II transposon carrying merA in oral streptococci highlights unique evolutionary pathways.
• The findings contribute to understanding the dissemination of mercury resistance in the human oral microbiome.