The microaerophilic nature of Wolinella recta, Wolinella curva, Bacteroides ureolyticus, and Bacteroides gracilis.
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Examination of the type strains of all Campylobacter species (except Campylobacter pylori), Wolinella recta, Wolinella curva, Bacteroides ureolyticus, and Bacteroides gracilis revealed that sheathed flagella occur only in species of rRNA group II (except W.succinogenes). This is helpful in differentiating this group.
Campylobacters are microaerophilic: they can respire with oxygen but cannot grow at the full level of oxygen found in an air atmosphere (21% 02). Although W. recta, W. curva, B. ureolyticus, and B. gracilis are closely related to the campylobacters of rRNA group I, they were thought to be anaerobes, incapable of oxygen-dependent growth and of respiring with 02. However, the present study revealed that they are in fact microaerophiles. They exhibited oxygen-dependent growth but failed to grow at 21% 02 and grew only very slightly under anaerobic conditions unless provided with electron acceptors such as fumarate and nitrate. They exhibited 02 uptake with H2 or formate as electron donors (W. recta showed only a low 02 uptake with H2). Oxygen uptake was inhibited by KCN and 2-heptyl-4-hydroxyquinoline N-oxide. The organisms possessed membrane bound cytochromes (cytochromes b560 and C551-553, and a CO-binding cytochrome c), as well as soluble cytochrome C552 and CO-binding cytochrome c. The cytochromes were reduced by H2 and formate as electron donors. Proton efflux from cells in anaerobic suspensions containing H2 or formate occurred upon addition of a pulse of oxygen. With formate as the electron donor, H+/O ratios of W. curva, W. recta, B. ureolyticus, and B. gracilis were 0.75, 1.66,2.06, and 2.04, respectively. With H2 as the electron donor, H+/O ratios of W.curva, B. ureoyticus, and B. gracilis were 1.25, 1.97, and 2.36, respectively; technical difficulties prevented measurement of the ratio in W. recta. Proton translocation was inhibited by the protonophore carbonylcyanide m-chlorophenylhydrazone. The results confirm the relationship of these organisms to campylobacters.
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