Isolation and Characterization of Aquaspirillum fasciculus sp. nov., a Rod-shaped, Nitrogen-Fixing Bacterium Having Unusual Flagella

Abstract

In 1971, Strength and Krieg reported the isolation of a gram-negative freshwater rod which exhibited bipolar flagellar fascicles clearly visible by dark-field microscopy. The flagellar fascicles exhibited helical wave propagation, basal bending, and an ability to coil up like springs. Despite the flagellar activity, the cells were apparently unable to swim freely. Such organisms appeared to be similar morphologically to an organism previously described by Houwink in 1953 and Jarosch in 1969. The present report describes a reliable isolation method for such organisms based on the use of L-proline and semisolid agar. Upon isolation, the organisms grew in flocs, from which a highly viscous matrix could be separated by high-speed centrifugation. After many transfers, the growth gradually became homogeneous and turbid, and the viscous substance could no longer be demonstrated. Under certain conditions of growth, steady straight-line motility could be observed and photographed within viscous flocs. Straight-line, free-swimming motility occurred in viscous suspensions of cells prepared by homogenization of flocs. In 8-to 12-h-old cultures in the nonviscous homogeneous condition, some cells could swim slowly in irregular, circular paths; other could move about on surfaces. When the viscosity of the medium was increased, nearly every cell could swim freely and steadily in straight paths. A viscosity of 200 centipoise was optimal for strain XI, whereas 10 centipoise was optimal for strains X and XU. These results suggest that the organisms may be highly adapted to life within viscous flocs. The organism exhibited nitrogenase activity when tested by methods developed by Dobereiner and her colleagues for "Spirillum" lipoferum; Aquaspirillum peregrinum also was found to possess nitrogenase activity. Investigation of the physiology and deoxyribonucleic acid base composition of strains X, XI, and XI1 has indicated that even though the organisms are straight rods, they are probably members of the genus Aquaspirillum. Important taxonomic considerations include: coccoid body or "microcyst" formation, possession of a "polar membrane" similar to that occurring in certain spirilla, bipolar tufts of flagella, a strictly respiratory metabolism, inability to attack carbohydrates, positive catalase and oxidase reactions, and a deoxyribonucleic acid base composition of 62 to 65 mol% guanine plus cytosine. The organisms were assigned to a new species, Aquaspirillum fasciculus, and the type strain was deposited with the American Type Culture Collection under the number 27740.In 1953, Houwink (11) described a "rod-like" bacterium which exhibited a "floundering" rather than a swimming type of motility. In resting specimens, both bipolar flagellar fascicles had the form of a coiled spring. The cells seldom moved more than a cell length, but in Present address:

Flagellum Density Regulates Proteus mirabilis Swarmer Cell Motility in Viscous Environments

“…Interestingly, E. coli cells were motile only in the lowest-viscosity motility buffers we used in P. mirabilis studies (i.e., 0.001 to 0.009 Pa · s). These results are not surprising, since the fluid viscosity required to inhibit cell motility varies between species and even between different isolates or phenotypes of the same species (17,20,61).…”

Intra- and Intergeneric Relationships of the Genus Aquaspirillum: Prolinoborus, a New Genus for Aquaspirillum fasciculus, with the Species Prolinoborus fasciculus comb. nov.

“…As a rod-shaped organism with nitrogenase activity, a DNA base composition of 62 to 65 mol% (compared with 49 to 52 mol% for A . serpens), and a remarkable type of locomotion (53,54), [A.] fusciculus can be differentiated easily from the other Aquaspirillum species.…”

“…Serological identification of most Spirillum species was possible by cross-agglutination with specific antisera prepared against Spirillum thermolabile antigens. The subsequent description of new species (lb, 5 , 34,38,53,58) and the use of improved tools for the taxonomic study of the spirilla have resulted in other identification routines.…”

“…The genus Aquaspirillum, with 13 species, was created for all of the aerobic freshwater spirilla, which had low salt tolerances and G+C contents of 50 to 65 mol%. Later, the genus Aquaspirillum was expanded by the addition of six new species (lb, 5 , 34,38,53,58). As mentioned by Krieg (30,31), this was an improvement over the previous classification, but it was still not entirely satisfactory.…”

Reclassification of Aquaspirillum itersonii and Aquaspirillum peregrinum as Novispirillum itersonii gen. nov., comb. nov. and Insolitispirillum peregrinum gen. nov., comb. nov.

“…The genus Aquaspirillum was created by Hylemon et al (1973) with the descriptions of 13 species and, subsequently, further Aquaspirillum species have been described (Kumar et al, 1974;Strength et al, 1976;Aragno & Schlegel, 1978;Maratea & Blakemore, 1981;Butler et al, 1989). However, many Aquaspirillum species have been transferred to other genera or reclassified as members of novel genera (Schleifer et al, 1991;Pot et al, 1992;Cleenwerck et al, 2003;Wauters et al, 2003;Ding & Yokota, 2004;Spring et al, 2004;Grabovich et al, 2006).…”