A bacterial cytokine

Area of Science:

• Microbiology
• Bacteriology
• Molecular Biology

Background:

• Dormant bacterial cells pose challenges in culture and detection.
• Micrococcus luteus produces a factor that aids in the revival of non-growing cells.
• This factor, the resuscitation-promoting factor (Rpf), is a purified protein.

Purpose of the Study:

• To characterize the Rpf protein from Micrococcus luteus.
• To investigate the effects of Rpf on dormant and growing bacterial cells.
• To explore the distribution and potential applications of Rpf and its related genes in other bacteria.

Main Methods:

• Purification of the resuscitation-promoting factor (Rpf) to homogeneity.
• Assaying Rpf's effect on viable cell counts of dormant M. luteus.
• Testing Rpf's growth-promoting activity on various bacterial species, including mycobacteria.
• Analyzing genome sequences and hybridization data for Rpf-like genes in Gram-positive bacteria.

Main Results:

• Rpf, a protein, promotes resuscitation and growth of dormant M. luteus cells at picomolar concentrations.
• Rpf significantly increases viable cell counts (over 100-fold) and stimulates growth.
• Rpf also stimulates the growth of several high G+C Gram-positive bacteria, notably mycobacteria (M. avium, M. bovis, M. kansasii, M. smegmatis, M. tuberculosis).
• Genes encoding Rpf homologs are widespread in high G+C Gram-positive bacteria, including Mycobacterium, Corynebacterium, and Streptomyces species.

Conclusions:

• Rpf is a potent bacterial growth factor with autocrine and paracrine functions.
• The widespread distribution of Rpf-like genes suggests conserved mechanisms for bacterial resuscitation and growth.
• Mycobacterial Rpf homologs represent potential targets for pathogen detection and control strategies.