STUDIES ON PATHOGENIC HALOPHILES

III. NUTRITIONAL REQUIREMENTS

Abstract

For the counting of viable marine bacteria, ZoBell(4) developed a medium composed of marine water, Bacto-peptone, ferric phosphate and Bacto-agar, to obtain the highest count of aerobic halophiles. However, he did not observe any increase in the number of viable cells with the addition of fish extract and glucose. Katz-nelson(5) studied the nutritional requirement of halophiles and observed that a halophilic Vibrio grew well in a basal medium composed of casamino acid, cystine, tryptophane, inorganic salts, succinate and citrate. Growth was stimulated by the addition of ribonucleic acid or its pyrimidines, uracil and cystosine. The halophilic Pseudomonas was somewhat favored by the presence or deoxyribonucleic acid. Similar results were observed by Flannery(8), who attempted the simplification of the syn-thetic medium for the cultivation of halophiles. The authors therefore concluded from the present experiment that the pathogenic halophiles, supposedly belonging to Pseudomonas or Vibrio, did not require definite essential factors. According to the results of Koser et al.(10). Robinson(11) and Ohsawa(12), Pseudomonas aeruginosa grew well in a medium containing no growth factors. It is well known that Vibrio choleraegrows well simply in peptone water, and Kuwahara(13) observed a stimulating effect of potassium α-naphthyl acetate on the growth of V. cholerae.
From the results of ZoBell(4) and Flannery(8), they conclude that the halophiles, presumably resembling our pathogens, usually grow well in peptone or casamino acids. In the present experiment, the authors concluded that strain N4 grows well in casein acidhydrolyte and slightly poorly in tryptophane plus cystine, and strain EB102 grows in casein acidhydrolyte but not in the other two amino-acids. Both of these strains can not utilize nitrate as a source of nitrogen. Although the patho-genic halophiles grew in a 3 per cent sodium chloride Simmons' citrate medium containing ammonium(3) as a sole source of nitrogen, succesive culture was not done at that time. In a synthetic medium containing 15 to 16 amino-acids, strain N4 grew well, while strain EB102 grew poorly in a few exception. This suggests that a favourable element is present in the casein acidhydrolyte to promote the growth of EB102. The effect of each amino-acid on the growth pattern was not studied in this elimination procedure, but it would be performed in the future using syn-thetic media containing fewer amino-acids.
The effects of various nitrogen source on P. aeruginosa were observed by Koser et al.(10) using ammonium; Robinson(11) on ammontum, nitrate and amino-acids; and Ohsawa(12) on ammonium and amino-acids, but not on nitrate. The capability of P. aeruginosa to assimilate ammonihm was confirmed by Hulton-Frandel et al.(14), Sandiford(15), and Young(16). Kuwahara(13) observed the growth of many strains of V. cholerae in a defined medium composed of ammonium, glucose and glutamic acid.