Growth enhancement and selection attempts for Spirillum volutans

Project objectives were to develop an improved plating medium to achieve reproducible colony counts and accurate quantification for growth or survival of Spirillum volutans; and to develop an improved method for selection of S. volutans from nature.

Growth enhancement studies began with casein hydrolysate-succinate-salts medium (CHSS). Casein hydrolysate concentration, type of casein hydrolysate, pH, and phosphate concentration optima were determined. Growth of S. volutans doubled after 24 h with the addition of potassium phosphate buffer (1 mM final concentration) to CHSS medium (CHSS-P). Addition of supplements to CHSS-P medium, and modified Bordetella and Brucella media failed to increase the cell yields of S. volutans. Punctiform colonies did form in CHSS-P medium (0.7% agar) pour-plates, yet at a recovery rate much lower than reported by Padgett et at. (1982) for surface growth on spread plates. The role of amino compounds as possible growth factors was investigated. Thin-layer chromatography, gas chromatography, and amino acid analysis were employed to identify those amino compounds (if any) that decreased or disappeared in the medium after 48 h of growth. None could be found. Numbers of viable cells were not greatly increased, however, viability was prolonged by growing S. volutans in dialysis sacs suspended in CHSS-P medium.

The tolerances of S. volutans to several antimicrobial compounds were determined. Attempts at using hay infusion, Pringsheim, and CHSS-P media supplemented with various compounds as selective agents did not result in predominance of S. volutans.