Corrosion induced by microorganisms is an already known fact that affects, among other heavy industries, the oil and gas sector. Its understanding and deep knowledge can avoid material and physical damage to those involved in the related processes. Molecular tools may help to mitigate these possible damages; however, studies are needed to understand molecular mechanisms involving microbial activity, especially the transcription of important enzymes such as sulfite reductase (dsrAB) which may be involved inthe corrosive process. mRNA extraction and cDNA synthesis were performed to quantify gene expression. Also, the enzyme production quantification by molecular techniques and H2S analysis were conducted to check dissolved gas concentration through potentiometric titration. It was possible to infer that availability of carbon sources and its complexity may increase bacterial metabolic activity, especially in the presence of lactate that, in this study, showed an increase in gene expression and H2S production compared to a variety of carbon sources and a control sample.