Helicobacter muridarum sp. nov., a Microaerophilic Helical Bacterium with a Novel Ultrastructure Isolated from the Intestinal Mucosa of Rodents

Abstract

Helical organisms with novel ultrastructural characteristics were isolated from the intestinal mucosa of rats and mice. These bacteria were characterized by the presence of 9 to 11 periplasmic fibers which appeared as concentric helical ridges on the surface of each cell. The cells were motile with a rapid corkscrewlike motion and had bipolar tufts of 10 to 14 sheathed flagella. The bacteria were microaerophilic, nutritionally fastidious, and physiologically similar to Helicobucter species and Wolinella succinogenes but could be differentiated from these organisms by their unique cellular ultrastructure. Using 16s rRNA sequencing, we found that strain STIT (T = type strain) was related to previously described Helicobucter species, "Flexispira rappini," and W . succinogenes. The closest relatives of strain STIT were Helicobacter mustelae and "F. rappini" (average similarity value, 96%). On the basis of phylogenetic data, strain STIT (= ATCC 49282T) represents a new species of the genus Helicobucter, for which we propose the name HeZicobucter muridarum.Bacteria with a variety of spiral morphologies are common inhabitants of the gastrointestinal tracts of both humans and animals (8-10, 20, 24-26, 30, 34, 39). Several of these spiral bacteria are helically coiled and possess bipolar tufts of flagella and concentric ridges that are due to periplasmic fibers that run the length of each cell. They have been seen in a variety of gastrointestinal preparations, including ceca (8) and ilea of rats (34), colons of mice (39), and gastric mucosa (26) and fundic glands of dogs and cats (20). Recently, organisms with a similar morphology have been implicated in ovine abortions (5, 21) and in intestinal diseases in animals and humans (1, 37).Much of the recent work on spiral bacteria has concentrated on Helicobacter pylori and other Campylobacter-like organisms because of the postulated association of these bacteria with human gastrointestinal disease (6,18,28,29). The taxonomy of this group of organisms is now being clarified. Recent phylogenetic work has resulted in the creation of the genus Helicobacter, and new species of this genus are rapidly being recognized (14, 17,32,33,36,40,43). Although three of the gastric helicobacters are very similar physiologically and show high degrees of similarity (96%) in their 16s rRNA sequences, these bacteria have very different morphologies (19,24,31). H. pylori is a relatively short organism with one or two turns in its spiral body, while Helicobacter musteleae is a short, slightly curved, rodshaped organism with an unusual flagellum configuration. In contrast, Helicobacter felis is 5 to 7 pm long and has a tightly spiralled body with five or six turns; it is entwined with a distinctive series of periplasmic fibers.The distinctive periplasmic fibers are not new to us because 10 years ago we observed similar structures on a bacterium isolated from a rat ileum (34). The same organism * Corresponding author.has been described previously in the elegant electron microscopic studies of Erland...

Motility in the epsilon-proteobacteria

“…In Salmonella, approximately 11 stator complexes interact with the peptidoglycan layer and 128 P-ring [28,52,53], but C. jejuni has 17 stator complexes positioned at considerably wider diameter. This is 129 also evident in both Helicobacter muridarumand Helicobacter felis, in which freeze-fracture studies revealed 130 approximately 17 'studs' [30,34] previously shown to be stator complexes [54]. Thus in the epsilon-131 proteobacteria imaged so far, additional stator complexes are positioned at a wider radius than in the enteric 132…”

“…To survive and maintain motility, H. pylori secretes a urease which breaks down urea to 80 form ammonium, raising local pH, and reverting mucous to a viscous fluid. SomeHelicobacter species such 81 as Helicobacter muridarum [34]and Helicobacter trogontum [35] also assemble distinctive helical 82 periplasmic non-flagellar ribs within their periplasm. The significance of these ribs is unclear, but may 83 further augment the spiral characteristics of these species, or reinforce cell shape in bacteria which may be 84 exposed to large torques that might otherwise buckle or mishape the cell.…”

“…The presence of epsilon-proteobacteria in oilfields [57,58] In sum these questions will add to our understanding of epsilonproteobacteria motility, but also fundamentals 182 of the mechanics of the bacterial flagellar motor, and molecular evolution. 183 proteobacterialflagellar motors for H. mustelae [37], C. coli [50], C. fetus(left) [49], (right) [50], (b) freeze-193 fracture images reveal 17 'studs' likely to be stator complexes in H. felis [30]and H. muridarium [34]. Highlights for Beeby, "Motility in the epsilon-proteobacteria"  Epsilon-proteobacteria inhabit animal digestive tracts or environmental niches.…”

Natural and experimental Helicobacter pullorum infection in Brown Norway rats

“…cause clinical disease in rats, causing colitis in naturally and experimentally infected nu/nu rats (Haines et al, 1998;Lee et al, 1992;Mendes et al, 1996). Our finding of natural H. pullorum infection in rats and the ability of H. pullorum to experimentally infect rats warrants further studies to determine whether wild rats are infected with H. pullorum and serve as reservoirs capable of contaminating food stuffs used for poultry or human consumption.…”

Monitoring a mouse colony for Helicobacter bilis using a Helicobacter-genus-specific nested PCR

“…During the past two decades, several Helicobacter species, including H. muridarum (Lee et al 1992), H. hepaticus (Fox et al 1994), H. bilis (Fox et al 1995), H. rodentium (Shen et al 1997), H. typhlonius (Franklin et al 1999(Franklin et al , 2001), H. ganmani (Robertson et al 2001) and Flexispira rappini have been isolated from laboratory mice. F. rappini was named on the basis of its morphology but appears to represent at least 10 Helicobacter taxa, some of which can be found in mice (Dewhirst et al 2000).…”