Twenty-four different patterns of single and multiple requirements for various B vitamins were demonstrated for 665 cultures of marine bacteria grown in a basal synthetic seawater medium enriched with phosphate, vitamin-free casamino acids, dextrose, and succinate. Among 114 thiamine-requiring isolates, 55 were unable to make the pyrimidine moiety, 19 required thiazole, 13 needed both thiazole and the pyrimidine moiety, while 27 organisms required thiamine o r thiamine pyrophosphate for growth. Among 142 biotin requirers, 22 had to be supplied with biotin, 60 could use either biotin o r biocytin, 54 were able to respond to either biotin, biocytin, or desthiobiotin. Only six cultures could not use biocytin, and required either biotin or desthiobiotin. Various responses of vitamin BI2 requiring cultures indicated special types of specificity for cyanocobalamin and analogues of this vitamin. Computer-sorting at the 0.66 similarity coefficient breaking point arranged a group of 104 isolates into eight clusters. The isolates having biotin o r thiamine requirements, single or in combination with other vitamin needs, appeared to be randomly scattered through the eight clusters. IntroductionIn an earlier paper on the nutritional relationships of neritic marine bacteria, methods for isolating and testing microorganisms for various growth factors were described, and it was reported that numerous isolates from the sea require exogenous supplies of six common B vitamins (Burkholder 1963). In the preliminary report, requirements of 1748 cultures were determined in a series of organic media, designed to show the needs for amino acids or B vitamins required to sustain growth. The general results obtained in that set of determinations were as follows: 29y0 of the cultures could grow in a medium (I) containing seawater enriched with phosphate, ammonium nitrate, and dextrose and succinate as carbon sources; 5% were able to grow in medium I provided that B vitamins, including biotin, thiamine, cyanocobalamin, pantothenate, nicotinic acid: and riboflavin, were added (medium 11); 20% grew in medium I supplemented with amino acids (medium 111); 21% grew in a medium made up of media I1 and I11 combined; while 25% were able to grow only in a rich isolation medium, containing complex materials, such as trypticase, soytone, and yeast extract. Among the iso-

Two aerobic, gramnegative, red-pigmented, rod-shaped bacteria were compared morphologically and physiologically with Serratia species, which they resembled superficially. The pigment produced by the marine isolates was shown to be similar to prodigiosin, the red pigment of S. marcescens . The isolates had a single polar flagellum, were oxidative, and did not produce acetoin from glucose or reduce nitrates, which made them distinct from both S. marcescens and S. marinorubra . The latter conformed well to the descriptions of S. marcescens in Bergey's Manual . The marine isolates displayed an absolute growth requirement for sea water or its equivalent. The growth requirement for sea water was replaced by sea-water levels of sodium, potassium, and magnesium chloride. Pigment was produced only when this salt mixture was further supplemented with calcium chloride. Neither sea water nor a high salt level was required for growth or prodigiosin synthesis by the Serratia species examined.