Carbon monoxide production from heme compounds by bacteria

Area of Science:

• Microbiology
• Biochemistry
• Heme Metabolism

Background:

• Microbial hemoprotein catabolism is crucial for understanding how bacteria process heme-containing molecules.
• Mammalian tissues degrade heme, but bacterial pathways remain less understood, particularly regarding carbon monoxide (CO) formation.

Purpose of the Study:

• To investigate carbon monoxide (CO) formation by bacteria from various heme compounds.
• To compare microbial heme degradation pathways with those in mammalian tissues.
• To identify bacterial species and conditions conducive to CO production from heme.

Main Methods:

• Incubation of hemolytic and nonhemolytic bacteria (Streptococcus mitis, Bacillus cereus) with heme substrates (erythrocytes, hemoglobin, myoglobin, hematin, etc.).
• Aerobic and anaerobic incubation conditions at 37°C for 18 hours.
• Quantification of evolved carbon monoxide (CO) using gas chromatography.

Main Results:

• No carbon monoxide (CO) was produced by any bacteria under anaerobic conditions.
• Aerobic incubation led to CO formation from all tested heme compounds by hemolytic Streptococcus mitis and Bacillus cereus.
• Nonhemolytic Streptococcus mitis did not produce CO. CO production was abolished when heme iron was absent (protoporphyrin) or replaced (copper hematoporphyrin).

Conclusions:

• Hemolytic bacteria can generate carbon monoxide (CO) from heme compounds exclusively under aerobic conditions.
• The presence of intact heme iron is essential for bacterial CO production from these substrates.
• This study elucidates a specific pathway in microbial hemoprotein catabolism, distinct from mammalian heme degradation.