Arsenic resistance determinants from environmental bacteria.

Area of Science:

• Environmental Microbiology
• Molecular Biology
• Bacterial Genetics

Background:

• Arsenic contamination poses environmental and health risks.
• Bacterial resistance to arsenic is mediated by specific genetic determinants.
• Understanding the prevalence and origin of these determinants is crucial for environmental monitoring and remediation.

Purpose of the Study:

• To investigate the presence and nature of arsenic resistance (ars) genes in environmental bacterial isolates.
• To determine the homology of these determinants to known arsenic resistance genes from Escherichia coli and Staphylococcus.

Main Methods:

• DNA:DNA hybridization assays were performed using probes derived from Escherichia coli and Staphylococcus arsenic resistance genes.
• Colony hybridization was used to screen 32 Gram-negative and 10 Gram-positive environmental bacterial isolates.
• Southern hybridization was employed to further characterize positive hybridization results.

Main Results:

• Eleven Gram-negative strains hybridized with Escherichia coli chromosomal arsenic resistance gene probes.
• One Gram-negative strain hybridized with an Escherichia coli plasmid arsenic resistance gene probe.
• No hybridization was observed with a probe specific to the arsA (ATPase) gene or with a Staphylococcus plasmid probe.
• Homology to chromosomal ars genes was primarily found within the bacterial chromosome, with one exception showing both chromosomal and plasmid hybridization.

Conclusions:

• DNA sequences homologous to Escherichia coli arsenic resistance chromosomal genes are widespread in environmental Gram-negative bacteria.
• These findings suggest common evolutionary origins or horizontal gene transfer of arsenic resistance determinants.
• The study highlights the prevalence of chromosomal arsenic resistance genes in environmental bacteria.