Effects of pH and Lactate on Hydrogen Sulfide Production by Oral Veillonella spp

Abstract

Indigenous oral bacteria in the tongue coating such as Veillonella have been identified as the main producers of hydrogen sulfide (H 2 S), one of the major components of oral malodor. However, there is little information on the physiological properties of H 2 S production by oral Veillonella such as metabolic activity and oral environmental factors which may affect H 2 S production. Thus, in the present study, the H 2 S-producing activity of growing cells, resting cells, and cell extracts of oral Veillonella species and the effects of oral environmental factors, including pH and lactate, were investigated. Type strains of Veillonella atypica, Veillonella dispar, and Veillonella parvula were used. These Veillonella species produced H 2 S during growth in the presence of L-cysteine. Resting cells of these bacteria produced H 2 S from L-cysteine, and the cell extracts showed enzymatic activity to convert L-cysteine to H 2 S. H 2 S production by resting cells was higher at pH 6 to 7 and lower at pH 5. The presence of lactate markedly increased H 2 S production by resting cells (4.5-to 23.7-fold), while lactate had no effect on enzymatic activity in cell extracts. In addition to H 2 S, ammonia was produced in cell extracts of all the strains, indicating that H 2 S was produced by the catalysis of cystathionine ␥-lyase (EC 4.4.1.1). Serine was also produced in cell extracts of V. atypica and V. parvula, suggesting the involvement of cystathionine ␤-synthase lyase (EC 4.2.1.22) in these strains. This study indicates that Veillonella produce H 2 S from L-cysteine and that their H 2 S production can be regulated by oral environmental factors, namely, pH and lactate.O ral malodor is due to metabolic products of bacteria in the oral cavity, particularly those living on the dorsum of the tongue (1, 2). Some cases of oral malodor are known to be linked with periodontitis (3, 4), and thus various periodontitis-related bacterial species have been detected in the tongue coating (5, 6). These findings also suggest that the tongue coating plays a role in the reservoir of such bacteria (5). Most of these bacteria have the ability to produce hydrogen sulfide (H 2 S), one of the major components of oral malodor (7,8). In a previous study (9), we focused on oral malodor in patients without oral diseases such as periodontitis or caries and found that the predominant H 2 S-producing bacteria were not periodontitis-related bacteria but were mainly indigenous bacteria of the oral cavity such as Veillonella and Actinomyces. Among these, Veillonella species, including V. atypica, V. dispar, and V. parvula, were dominant (9).Veillonella species are Gram-negative anaerobic micrococci that are frequently detected in the tongue coating (6, 9). These bacteria are asaccharolytic but utilize lactate, pyruvate, and oxaloacetate as energy sources. Although several studies have reported that Veillonella species produce H 2 S (1, 8, 10, 11), the metabolic properties of H 2 S production have not been fully understood. In the tongue coating, environmen...

Integrated hypothesis of dental caries and periodontal diseases

“…In this environment, Veillonella species, which are lactate-utilizing and acid-tolerant anaerobes, can become dominant. Veillonella species are also eminent producers of hydrogen sulfide in the presence of lactate at acidic pH [62]. ) [63].…”

Oral malodorous gases and oral microbiota: From halitosis to carcinogenesis

“…Washio et al investigated the production of hydrogen sulfide from L-cysteine by growing cells, resting cells, and cell extracts of oral Veillonella species, as well as the effects of oral environmental factors, including pH and lactate [29]. The production of hydrogen sulfide was increased by lactate in the resting cell suspension but not in the cell extract, suggesting that it is caused by lactate activity; not the enzyme itself, but rather the process occurring prior to L-cysteine degradation, such as the incorporation of L-cysteine across the cell membrane.…”

“…A major contributor to ammonia in mouth-exhaled breath is oral bacteria or their enzymatic activity. Ammonia is produced by various amino acid-degrading oral bacteria, both indigenous bacteria, such as Veillonella [29], and periodontitis-associated bacteria, such as P. gingivalis [35], Prevotella intermedia [36] and F. nucleatum [37]. Ammonia is also produced from the urea caused by bacterial urease in the oral cavity [38].…”

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“…Nevertheless, under various circumstances, oral homeostasis is lost and certain species from these and other genera, such as Haemophylus, Lactobacillus and Porphyromonas, turn out to be opportunistic and can represent a potential threat for both oral and respiratory tract health status (Caufield, Li, Dasanayake, & Saxena, 2007;Washio, Shimada, Yamada, Sakamaki, & Takahashi, 2014;Zarco et al, 2012).…”