Anaerobic degradation of hydroaromatic compounds by newly isolated fermenting bacteria

Abstract

Aerobic organisms degrade hydroaromatic compounds via the hydroaromatic pathway yielding protocatechuic acid which is further metabolized by oxygenase-mediated ring fission in the 3-oxoadipate pathway. No information exists on anaerobic degradation of hydroaromatics so far. We enriched and isolated from various sources of anoxic sediments several strains of rapidly growing gram-negative bacteria fermenting quinic (1,3,4,5-tetrahydroxy-cyclohexane-1-carboxylic acid) and shikimic acid (3,4,5-trihydroxy-l-cyclohexene-1-carboxylic acid) in the absence of external electron acceptors. Quinic and shikimic acid were the only ones utilized of more than 30 substrates tested. The marine isolates formed acetate, butyrate, and H2, whereas all freshwater strains formed acetate and propionate as typical fermentation products. Aromatic intermediates were not involved in this degradation. Characterization of the isolates, fermentation balances for both hydroaromatic compounds, and enzyme activities involved in one degradation pathway are presented.

Psychrilyobacter atlanticus gen. nov., sp. nov., a marine member of the phylum Fusobacteria that produces H2 and degrades nitramine explosives under low temperature conditions

“…Table 1. Properties of strain HAW-EB21 T that distinguish it from the genera Propionigenium, Ilyobacter and Fusobacterium of the phylum Fusobacteria Taxa: 1, strain HAW-EB21 T ; 2, Propionigenium [data for Propionigenium maris (Janssen & Liesack, 1995;Watson et al, 2000) and Propionigenium modestum (Schink & Pfennig, 1982)]; 3, Ilyobacter [I. polytropus (Stieb & Schink, 1984), I. tartaricus (Schink, 1984) and I. insuetus (Brune & Schink, 1992)]; 4, Fusobacterium (Robrish et al, 1991;Hofstad, 1991;Moore et al, 1984). +, Positive; 2, negative; V, variable among species; NK, not known.…”

Ilyobacter insuetus sp. nov., a fermentative bacterium specialized in the degradation of hydroaromatic compounds.

“…Cultivation was performed routinely in oxygen-free, bicarbonate-buffered mineral medium with 5 mM sodium quinate (1,3,4,5-tetrahydroxy-cyclohexane-1-carboxylic acid, sodium salt) as the sole source of carbon and energy. Details are given in the original description (Brune & Schink, 1992 Additional growth tests on -glucose (5 mM), disodium -malate, disodium fumarate and sodium -lactate (each 10 mM) performed in medium supplemented with -phenylalanine, -tyrosine and -tryptophan (each 50 µM) were negative. This indicates that the absence of growth on these compounds is not caused simply by an inability of strain VenChi2 T to synthesize aromatic amino acids in the absence of quinate and shikimate as precursors.…”

“…This indicates that the absence of growth on these compounds is not caused simply by an inability of strain VenChi2 T to synthesize aromatic amino acids in the absence of quinate and shikimate as precursors. Other physiological properties of strain VenChi2 T have been documented in detail (Brune & Schink, 1992) ; taxonomically relevant traits are summarized in the species description (see below).…”

“…As precursors of lignin and tannin biosynthesis, quinic acid and shikimic acid are stored in considerable amounts in the vacuoles of many vascular plants (Yoshida et al, 1975). Aerobic bacteria and fungi degrade hydroaromatic compounds oxidatively via the hydroaromatic pathway, involving aromatic intermediates (for references, see Brune & Schink, 1992). The GenBank/EMBL accession numbers for the 16S and 23S rRNA gene sequences of strain VenChi2…”

“…A detailed morphological and physiological characterization of two of these isolates, the marine strain VenChi2 T and the freshwater strain GolChi1, has been published (Brune & Schink, 1992). Both strains were found to degrade hydroaromatic compounds via novel, fermentative pathways that do not involve aromatic intermediates (Brune & Schink, 1992).…”