Nitrite Accumulatin during Anaerobic Nitrate Reduction by Binary Suspensions of Bacteria Isolated from the Achlorhydric Stomach

Abstract

Binary suspensions of bacteria isolated from the gastric juice of achlorhydric patients were used to determine conditions which favour nitrite accumulation during nitrate reduction. Suspensions of Veillonella parvula and Haemophilus parainzuenzae accumulated nitrite during nitrate reduction in the absence of nitrite-reducing Neisseria subflava or Streptococcus sanguis.The maximum concentration of nitrite that transiently accumulated decreased predictably as the ratio of nitrite-removing bacteria to nitrite-accumulating bacteria increased. This ratio, but more importantly the bacterial density, determined the duration of nitrite accumulation. These results are correlated with the previously reported tendency of nitrite to accumulate in the gastric juice of hypogammaglobulinaemic and pernicious anaemic patients, and with the extremely high incidence of gastric cancer in the two groups.

Bacterial overgrowth and diversification of microbiota in gastric cancer

“…Bacterial overgrowth in the stomach has been found in various precancerous conditions 13 , 27 , including hypochlorhydria and mucosal atrophy. It has been suggested that microbes in the stomach are involved in the production of carcinogens and promotion of inflammatory injuries 15 , 28 Thus, bacterial overgrowth is a potential cancer-promoting factor 17 . Nonetheless, further studies are indicated to clarify whether the bacterial overgrowth is a consequence of cancerous mucosa that generates environments favoring bacteria proliferation.…”

“…Nitric oxide, a final product of nitrite reduction, is intensively involved in the protection of mucosal integrity 43 . Importantly, N-nitroso compounds derived from metabolisms of nitrate/nitrite are potent carcinogens 15 , 16 . E. coli , Lactobacillus , and Nitrospirae are all known to play a role in the metabolisms of nitrate/nitrite 42 , 44 , 45 .…”

“…Using culture-dependent approaches, bacterial overgrowth in the stomach has been found with a lowered acid output 13 , 14 . These bacteria potentially promote the production of nitrite, leading to accumulation of carcinogenic N-nitroso compounds 15 , 16 . Thus, it has been supposed that overgrowth of bacteria contributes toward the development of gastric cancer 17 .…”

Review article: proton pump inhibitors and bacterial overgrowth

“…As both bacterial overgrowth and the persistence of swallowed nitrite are related to elevated gastric pH it is not necessary to postulate that gastric bacterial activity alone produces higher levels of intragastric nitrite. The fact that intragastric pH and not bacterial metabolism is the cause of raised intragastric nitrite levels is supported by the in vitro work of Forsythe and coworkers 25, 26 who showed that in a mixed culture of bacteria containing nitrate and nitrite‐reducing bacteria the concentrations of nitrite will initially rise but subsequently fall as nitrite reducing bacteria further reduce nitrite. If the achlorhydric stomach is stably colonized by a metabolically active bacterial flora then a steady state high nitrite system should not exist.…”

Microbes involved in dissimilatory nitrate reduction in the human large intestine

“…The observation that bacteria from the human large intestine are capable of nitrate reduction [9,15–17], coupled with the fact that this anaerobic environment is highly fermentative, suggests that the process may have significance in humans. Allison and Macfarlane [9] showed that the addition of 10 mM KNO 3 to human faecal slurries, supplemented with either starch or casein, significantly reduced H 2 and CH 4 production.…”