Hemin-dependent growth stimulation and cytochrome synthesis in Corynebacterium pyogenes

The iron-regulated iupABC operon is required for saprophytic growth of the intracellular pathogen Rhodococcus equi at low iron concentrations

Rhodococcus equi is a facultative intracellular pathogen which proliferates rapidly in both manure-enriched soil and alveolar macrophages. Although both environments are characterized by extremely low concentrations of free iron, very little is known regarding the strategies employed by R. equi to thrive under these conditions. This paper reports the characterization of an R. equi transposome mutant that fails to grow at low iron concentrations. The transposome was shown to be inserted into iupA, the first gene of the iupABC operon encoding an ABC transport system highly similar to siderophore uptake systems. Disruption of the iupA gene also resulted in a failure of R. equi to utilize heme and hemoglobin as a source of iron. Introduction of the iupABC operon in trans restored the wild-type phenotype of the mutant strain. iupABC transcripts were 180-fold more abundant in R. equi grown in iron-depleted medium than in organisms grown in iron-replete medium. Proliferation of the iupABC mutant strain in macrophages was comparable to that of the wild-type strain. Furthermore, the iupABC mutant was not attenuated in mice, showing that the iupABC operon is not required for virulence.

Nutritional requirements of Corynebacterium pyogenes

The nutritional requirements of Corynebacterium pyogenes (strains C100, 5, and 1909), a commonly encountered animal pathogen, were determined in this study. A semidefined medium (SDM) containing glucose, HCO3-, hemin, charcoal-treated Trypticase, and a defined mixture of purines and pyrimidines, amino acids, and minerals which supported optimal growth of C. pyogenes was employed in all nutritional studies. Adenine and uracil were required for optimal growth of strains 5 and C100 but were not required for strain 1909. Riboflavin and nicotinic acid were required for good growth of all three strains; biotin and thiamin were stimulatory but did not appear to be required for growth. Hemin and NaHCO3 were stimulatory for growth, whereas lipoic acid and Tween 80 were neither stimulatory nor required for growth. The replacement of Trypticase with a specific peptide fraction (obtained by fractionation of Trypticase on Sephadex G-25) rich in dipeptides gave growth comparable to that in SDM, indicating a peptide requirement for the growth of C. pyogenes. It was of considerable interest that growth comparable to that in SDM was obtained when Trypticase was replaced by inositol (1 microgram/ml of SDM).

Value of acid metabolic products in identification of certain corynebacteria

Acid metabolic products of 23 strains of human and animal pathogenic corynebacteria, representing eight different species, were determined by gas chromatography. The results showed that the species examined were metabolically heterogeneous and could be presumptively identified based on the acid products produced. Corynebacterium equi did not produce any acids; C. renale produced lactate; and C. pyogenes produced major amounts of lactate, variable amounts of acetate, and minor amounts of succinate and pyruvate. C. kutscheri produced propionate and lactate as major products and pyruvate and oxalacetate as minor products. C. diphtheriae and C. pseudotuberculosis produced major amounts of propionate, acetate, and formate. In addition, C. pseudotuberculosis produced major amounts of pyruvate and minor amounts of succinate, lactate, and oxalacetate, whereas C. diphtheriae strains produced minor but variable amounts of lactate, succinate, fumarate, pyruvate, and oxalacetate. C. bovis produced aicd products similar to those of C. pyogenes but was readily distinguishable from the latter by the lack of hemolysis on blood agar, colony morphology, catalase reaction, and biochemicals. C. suis characteristically produced major amounts of ethanol, acetate, and formate and minor amounts of lactate and succinate but no propionate.