Genes required for cytochrome c synthesis in Bacillus subtilis

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Cytochromes c, essential for cellular respiration, possess covalently bound haem and are located on the periplasmic side of the cytoplasmic membrane in bacteria.
• While Gram-negative bacteria utilize over eight specific gene products for cytochrome c biogenesis, homologous genes are absent in Gram-positive bacteria.

Purpose of the Study:

• To identify novel genes involved in cytochrome c biogenesis within the Gram-positive bacterium Bacillus subtilis.
• To investigate the function of identified genes and their role in the cytochrome c synthesis pathway.
• To compare the cytochrome c synthesis machinery in Gram-positive bacteria with other organisms.

Main Methods:

• Employed two random mutagenesis approaches to screen for essential genes in Bacillus subtilis.
• Utilized gene inactivation attempts to assess the viability and function of identified genes.
• Analyzed the effects of mutations on cytochrome c synthesis, sporulation, and growth.

Main Results:

• Identified three genes: resB, resC, and ccdA, crucial for cytochrome c biogenesis in Bacillus subtilis.
• Demonstrated that mutations in resB or resC specifically block cytochrome c synthesis without significantly impacting other cytochromes, sporulation, or growth.
• ResB and ResC, previously uncharacterized membrane proteins, show sequence similarity to proteins involved in chloroplast cytochrome c synthesis.

Conclusions:

• The findings strongly support the existence of a similar cytochrome c synthesis system (System II) in Gram-positive bacteria, cyanobacteria, epsilon-proteobacteria, and chloroplasts.
• This system (System II) is mechanistically distinct from the systems found in most Gram-negative bacteria (System I) and mitochondria (System III).
• ResB and ResC are essential components of the System II cytochrome c biogenesis machinery.