Methanogenic bacteria from human dental plaque

Abstract

Samples of human dental plaque were examined for the presence of methanogenic bacteria. Of 54 samples from 36 patients, 20 yielded H2/CO2-using methanogenic enrichment cultures. All methanogen-positive samples were from patients with some degree of periodontal disease. The predominant populations in the enrichments had morphologies characteristic of Methanobrevibacter spp. In six enrichments derived from three patients, the common methanogen was antigenically similar to Methanobrevibacter smithii. The same was true for the three methanogenic isolates obtained in axenic culture from a fourth patient. The six enrichments and two of the three isolates were antigenically closer to strain ALI than to PS. Two of the enrichments also had subpopulations with weak antigenic similarity to Methanosphaera stadtmanae. The data indicate that methanogens in the oral cavity of humans are antigenically close to those found in the intestinal tract. Methanogenic bacteria belong to the group of organisms known as the archaebacteria (2, 9). They are strict anaerobes characterized by the ability to produce methane from H2/CO2 and, in some cases, from formate, acetate, methanol, or methylamine. Methanogenic bacteria have been isolated from sewage sludge, lake sediments, hot springs, and the intestinal tracts of animals, including humans. About one-third of the adult human population in the United States is reported to carry methanogens in the large intestine, with Methanobrevibacter smithii being the predominant methanogen present (5, 6, 18). However, the presence of methanogens in the human oral cavity has not been examined. Recently, the presence of methanogens in dental-plaque samples from monkeys was reported (13). We describe in this report our examination for methanogens in subgingival dental-plaque samples from patients at the

The domain Archaea in human mucosal surfaces

“…Human microbiome studies have revealed that archaea colonize distinct niches in the human body, arranged in complex communities [24][25][26][27]. Archaea are mainly found in the gut [13,14,[28][29][30] and the oral cavity [11,12,[31][32][33].…”

Identification of archaeal rDNA from subgingival dental plaque by PCR amplification and sequence analysis

“…Previously, three studies reported methane production in enrichment cultures from human dental plaque. Methanogenesis occurred in subgingival plaque from 10 out of 36 [6] and from three out of 10 [7] periodontitis patients and in dental plaque from nine out of 20 healthy individuals [8]. Enriched bacteria were assigned to the genus Methanobrevibacter by phenotypic and immunological methods [6,7] and an oral isolate was described as Methanobrevibacter oralis [9].…”

Laboratory tools for detection of archaea in humans

“…A second methanoarchaeon isolated from human faeces was Methanosphaera stadtmanae; Miller and Wolin [8] have established that this archaeon requires H 2 and methanol for growth, and uses H 2 to reduce methanol to methane. In a further study, Belay et al [48] succeeded in isolating strains having antigenic similarity with M. smithii and Methanosphaera stadtmanae from samples related to patients with some degree of periodontal disease. Thereafter, anaerobic sampling and culture of 12 vaginal specimens collected from eight healthy women, three women with bacterial vaginosis and one women with erosive lichen planus yielded methanoarchaea in only two of the specimens from patients with bacterial vaginosis.…”

“…It is well established that archaea and, especially, methanoarchaea inhabit humans, and high numbers have been found in the colon, mouth, and vagina. M. smithii, Methanosphaera stadtmanae, M. oralis and 'Methanomassiliicoccus luminyensis' have been, until now, the only four archaeal organisms isolated in humans by culture approaches [2,[7][8][9]17,48,49] (B. Dridi et al, unpublished data). The prevalence and quantity of human gut methanoarchaea have been underestimated for a long time, undoubtedly because of the complicated nature of their cultivation and the fact that standard protocols for DNA extraction have not been optimized for such fastidious microorganisms.…”