Aquaspirillum Serpens Research Articles

Defined medium for Aquaspirillum serpens VHL effective in batch and continuous culture.

A defined medium for Aquaspirillum serpens VHL allows the replacement of the complex media now in use. It was developed by batch culture methods but supports growth in continuous culture. A basal salts medium supplemented with L-aspartic acid, L-alanine, and L-glutamic acid provided the best growth (turbidity), as long as ammonium chloride was omitted. Ammonium chloride caused either a lag or a reduction or a complete inhibition of the growth of A. serpens VHL on the above amino acids and other organic supplements depending on the combination used. Ammonium sulfate and ammonium hydroxide with L-glutamic acid allowed growth, but the lag period was increased in shake flask cultures. Vitamins, cysteine hydrochloride, and carbon dioxide had no effect on the growth rate. Viability (less than 50%) was inadequate to maintain continuous culture with L-glutamic acid as the sole source of carbon and nitrogen. Combinations of amino and carboxylic acids were then tested and, of these, L-glutamic acid (1 g/liter) and L-histidine (75 mg/liter) without ammonium chloride in the basal salts medium supported growth in batch and continuous culture. L-Glutamic acid was the limiting substrate for growth.

Identification of an outer membrane-associated protein of Aquaspirillum serpens by immunoelectron microscopy

Identification of an outer membrane-associated protein of Aquaspirillum serpens by immunoelectron microscopy

Electron microscopy of malachite green--glutaraldehyde fixed bacteria.

Malachite green combined with glutaraldehyde has been used recently as a fixative for preserving and revaling lipid complexes in thin sections of eukaryotic cells examined by electron microscopy. When bacteria were prefixed with the above mixture granular electron dense inclusions were revealed in all cultures tested. These inclusions were replaced by electron transparent areas in cells fixed with glutaraldehyde alone. The structures were frequently located near to or within the nucleoid and adjacent to the cell membrane in Gram-negative bacteria and were associated with the nucleoid and mesosomes in Gram-positive species. Polyhydroxybutyrate granules, generally poorly preserved in thin sections of Aquaspirillum serpens, were well preserved by the malachite green-glutaraldehyde fixative. Malachite green complexes were observed outside of the cells in all preparations. Capsules were neither preserved nor stained.

Cell envelope associations of Aquaspirillum serpens flagella.

Specific regions of the cell envelope associated with the flagellar basal complex of the gram-negative bacterium Aquaspirillum (Spirillum) serpens were identified by studying each of the envelope layers: outer membrane, mucopeptide, and plasma membrane. The outer membrane around the flagella insertion site was differentiated by concentric membrane rings and central perforations surrounded by a closely set collar. The perforations in both the outer membrane and the isolated mucopeptide layer were of a size accomodating the central rod of the basal complex but smaller than either the L or the P disks. The P disk of the complex may lie between the mucopeptide and the outer membrane. Electron microscopy of intact, spheroplasted, or autolyzed preparations did not adequately resolve the location of the inner pair of disks of the basal complex. Freeze-etching, however, revealed differentiation within the plasma membrane that appeared to be related to the basal complex. The convex fracture face showed depressions which are interpreted as impressions of a disk surrounded by a set of evenly spaced macromolecular studs and containing a central "plug" interpreted as the central rod. In thin sections, blebs, which appear to be associated with the flagellar apparatus, were seen on the cytoplasmic side of the plasma membrane. Superimposing the dimensions of the flagellar basal complex and the spacings of the cell envelope layers and using the position of the L disk within the outer membrane for reference, showed that the S disk might be within and the M disk beneath the plasma membrane. A tentative model was developed for comparison with that based on the structure of the Escherichia coli basal complex.

Isolation, Characterization, and Taxonomy of Aquaspirillum bengal sp.nov.

A large spirillum was isolated from a freshwater pond in West Bengal. Its deoxyribonucleic acid base composition (51 mol% guanine + cytosine) and cell diameter (0.9 to 1.2.) were similar to those of Aquaspirillum serpens and A. putridiconchylium. Although its characteristics corresponded more closely to those of the latter species than of any other, the spirillum is unique in having an unusually high temperature for optimal growth (41 C), in forming water-soluble pigments from tyrosine and tryptophan, and in several other nutritional, biochemical, and serological characteristics. On the basis of these differences, the isolate was proposed as a new species,Aquaspirillum bengal. The type strain was deposited with the American Type Culture Collection under the number 27641.