Violet-pigmented bacteria isolated from the estuarine waters of Waccasassa Bay, Fla., were found to have biochemical and physiological characteristics very similar to those of Alteromonas luteoviolacea Gauthier 1982. All isolates tested had sheathed flagella, which seem to exclude them from the genus Alteromonas Baumann et al. 1972 as presently described. We suggest altering the genus description to include strains with this characteristic.

An L-arabino-aldose dehydrogenase responsible for the oxidation of L-arabinose to L-arabino-γ-lactone has been purified 59-fold from L-arabinose grown cells of Azospirillum brasiliense. The dehydrogenase was found to be specific for substrates with the L-arabino-configuration at carbons 2, 3, and 4. Km values for L-arabinose of 75 and 140 μM were found with NADP and NAD as coenzymes, respectively. The enzyme had a pH optimum of 9.5 in glycine buffer and was stable when heated to 55 °C for 5 min. No enhancement of activity in the presence of any divalent cation or reducing agent tested was found. L-Arabinose dehydrogenase had a molecular weight of 175 000 as measured by the gel filtration technique.

An oxidative pathway by which L-arabinose is converted to alpha-ketoglutarate in crude extracts of Azospirillum brasiliense is demonstrated. Specific activities of enzymes involved in the pathway were determined, and several pathway intermediates were identified.

Azospirillum brasilense was reisolated from associations with callus tissue cultures of sugarcane and compared with stock cultures of the inoculated bacterium and related strains. Although the reisolate had a growth rate similar to stock cultures, it exhibited a severalfold increase in maximum specific activity of nitrogenase. The reisolate and the parent culture had similar ultrastructure. The general ultrastructure of Azospirillum is described. The bacterium was capsulated when grown on nitrogen-free nutrient agar plates and on callus, but was not capsulated when growing in a subsurface zone in N-free semisolid nutrient agar, except rarely in aging cultures. Capsulation may be a protective mechanism against unfavorable pO 2 under dinitrogen-fixing conditions. Pleomorphism occurred in capsulated forms, and the ultrastructure of these forms is described.

We have isolated Azospirillum (Spirullum lipoferum) from roots of grasses of several genera collected from a number of tropical and subtropical-temperate locations. Pure cultures were obtained from a small percentage of samples; no higher percentage was secured from tropical than from other grasses. Acetylene reduction and distinctive growth in N-free soft agar deeps were inadequate to identify this genus, although helpful in initial screening. Fluorescent antibody tests with antiserum against characterized strains were helpful. There is some evidence that this genus of bacteria may be favored in the rhizoplane.

Field-grown pearl millet ( Pennisetum americanum ) and guinea grass ( Panicum maximum ), lightly fertilized and inoculated with Spirillum lipoferum , produced significantly higher yields of dry matter than did uninoculated controls. Up to 42 and 39 kilograms of nitrogen per hectare were replaced by inoculation for pearl millet and guinea grass, respectively. The data demonstrate that nitrogen fixation by these grass- Spirillum systems is efficient and is achieved at a reasonable energy cost to the plant.

Sud , I. J. (University of Florida, Gainesville), and M. E. Tyler . Cell-wall composition and osmotic fragility of selected marine bacteria. J. Bacteriol. 87: 696–700. 1964.—Cell-wall composition of three marine pseudomonads, selected to represent a spectrum of osmotic fragilities, was determined and compared with that of Pseudomonas aeruginosa . The walls of the marine bacteria were composed predominantly of lipoprotein. No sugars, except glucosamine, were detected, and the reducing values were similar to the respective hexosamine values. These varied from 0.9 to 1.8%, the most osmotically fragile marine bacterium possessing the lowest amount of hexosamine in the wall. Possible relationship between wall hexosamine content and osmotic fragility was indicated.

SUMMARY: Marine bacteria from Atlantic coastal waters off Florida, isolated by a technique assuring that all would grow on a sea-water medium but not on a distilled water medium, were studied; 96 of 100 original isolates were characterized by morphological and some physiological properties, particularly those related to mineral responses. All isolates were Gram-negative rods or spiral forms, grew well in a simple saline-peptone medium, and most were pigmented and motile. All isolates required NaCl for good growth, and groupings could be clearly established for those whose mineral nutrition was satisfied, in a casein digest broth, by adding NaCl only, NaCl + KCl, NaCl + Mg salts, or all three salts. Lytic susceptibility in various mineral solutions and growth tolerance to various salt levels were studied. Some overall similarities, and a few correlations between mineral nutrition and physiological versatility, were established.