Fermentation of tartrate enantiomers by anaerobic bacteria, and description of two new species of strict anaerobes, Ruminococcus pasteurii and Ilyobacter tartaricus

Abstract

Enumerations of tartrate-fermenting anaerobic bacteria with l-, d-, and m-tartrate as substrates revealed that l-tartrate fermenters outnumbered d- and m-tartrate fermenters by one to three orders of magnitude in all three anoxic environments studied. Highest numbers of tartrate-fermenting bacteria were found in freshwater creek sediments, less in polluted marine channels, and lowest numbers in anoxic sewage digestor sludge. Prevailing bacteria were isolated on every tartrate enantiomer. They all degraded tartrates via oxaloacetate. d- and m-tartrate-fermenting anaerobes were able to ferment l-tartrate as well, and were assigned to the genera Bacteroides, Acetivibrio, and Ilyobacter. l-Tartrate-fermenting anaerobes only utilized this enantiomer, and were characterized in more detail. Fermentation products on tartrate, citrate, pyruvate, and oxaloacetate were acetate, formate, and carbon dioxide. On fructose and glucose, also ethanol was formed. Freshwater isolates were Gram-positive cocci with large slime capsules, and were described as a new species, Ruminococcus pasteurii. Saltwater isolates were Gram-negative short rods, and were also described as a new species, Ilyobacter tartaricus. The guanosine-plus-cytosine content of the DNA was 45.2% and 33.1%, respectively.