Aquaspirillum

Abstract

Aq.ua.spi.ril' lum . L. aqua water; Gr. n. spira a spiral; N.L. dim. neut. n. spirillum a small spiral; Aquaspirillum a small water spiral. Proteobacteria / Betaproteobacteria / Neisseriales / Neisseriaceae / Aquaspirillum Rigid , helical cells , 0.2–1.4 µm in diameter; however, one species is vibrioid and one species contains straight‐to‐curved rods. A polar membrane underlies the cytoplasmic membrane at the cell poles in all species so far examined for this characteristic by electron microscopy. Intracellular poly ‐β‐ hydroxybutyrate is formed, except in two species. Some species form thin‐walled coccoid bodies, which predominate in cultures of three to four weeks. Gram negative . Motile by polar flagella , generally bipolar tufts ; one species is monotrichous, others have a single flagellum at one or at each pole. Aerobic to microaerophilic , having a respiratory type of metabolism with oxygen as the terminal electron acceptor ; a few species can grow anaerobically with nitrate. The optimal growth temperature for most species is 30–32°C. Chemoorganotrophic ; however, one species is a facultative hydrogen autotroph. Oxidase positive . Usually catalase and phosphatase positive . Indole and sulfatase negative . Casein, starch, and hippurate are not hydrolyzed. No growth occurs in the presence of 3% NaCl. A few species can denitrify. Nitrogenase activity occurs in some species, but only under microaerobic conditions. Carbohydrates are not usually metabolized, but a few species can attack a limited variety. Amino acids or the salts of organic acids serve as carbon sources. Vitamins are not usually required. Usually occur in stagnant, freshwater environments. The mol % G + C of the DNA is : 49–66. Type species : Aquaspirillum serpens (Müller 1786) Hylemon, Wells, Krieg and Jannasch 1973b, 366 (“ Vibrio serpens ” Müller 1786, 48.)

Interactions between plants and soil shaping the root microbiome under abiotic stress

“…This change in O 2 availability can then result in a progressive shift in the microbial community from aerobic organisms, to facultative anaerobes, and finally to strict anaerobes [62]. This shift toward anaerobic bacteria was hypothesized to be one possible explanation behind the increase in the relative abundance of Aquaspirillum in flooded poplar rhizosphere and root samples, as the genus contains a few known anaerobic species [58,63].…”

“…However, possible effects of exudation of phytotoxic and other compounds on root-associated bacterial communities also remain unexplored. Graff and Conrad [58] hypothesized that the previously mentioned increase in relative abundance of Aquaspirillum, a bacterial genus with known ethanol catabolizing species [63], in flooded poplar rhizosphere and root samples could be due to the exudation of ethanol from roots, a known oxygen stress tolerance mechanism of poplar, as well as to the decrease in O 2 availability.…”