Peptide and Amino Acic Oxidation in the Presence of Thiosulfate by Members

Themzoanaerobacter brockii, T, etltanolicus, T. themzohydrosuljüricus, T. jìnnii, and Thennoanaerobacter strain SEBR 5268 (an isolate from an oil-producing well) were studied for their ability to oxidize proteinaceous compounds that included gelatin, peptides, and casamino acids. All bacteria tested used peptides and amino acids, but only slightly. However, in the presence of thiosulfate all the Tlzennoanaerobacter species showed a substantial improvement in growth and/or the production of acetate, isovalerate, isobutyrate, and sulfide. Propionate was a minor product of peptide or amino acid oxidation. The reduction of thiosulfate during growth on peptides by members of the Themzoanaerobacter species is a trait that closely resembles that of archaeal hyperthermophiles during growth on peptides and amino acids with elemental sulfur as electron acceptor. In the past two decades, novel thermophilic microbes, which include members of the domains Archaea and Bacteria, have been isolated from a variety of thermal environments [17,24]. In the case of members of the domain Bacteria, a great deal of attention has been focused on thermoanaerobes, e.g., Clostridium themzohydrosuljüricum, Themzoanaerobacter species, and Themzoanaerobium species as they have potential in the fuel and enzyme industries [17, 271. On the basis of the current knowledge, strains of Clostridium themzolzydrosuljüricum and Themtoanaerobium brockii have recently been reclassified and are all now included as members of the genus Themzoanaerobacter [ 161. Themzoanaerobacter species are thermophilic, heterotrophic, saccharolytic anaerobes and have the ability to reduce thiosulfate to sulfide. Their habitat is soil, sugar beet extraction juices, sugar cane juices, thermal volcanic hot springs, and oil-producing wells [9, 16, 211. In the domainhchaea, numerous studies have been undertaken on the novel and presumably archaeal nature of their physiology, which includes growth on peptides and/or amino acids and the concomitant reduction of sulfur in order to gain Correspondence to: B. Ollivier energy for growth [l, 181. Proteolytic, peptidolytic or aminolytic activities have also been demonstrated in the mesophilic and thermophilic anaerobes in the Bacteria domain. Of these, mesophilic bacteria belonging to the genera Clostridìuin and Bacteroides have been the most intensively studied with respect to their role in mineralizing proteins [8, 111. Themobacteroides proteotyticus [20], recently renamed as Coprothetmobacter proteotyticus [22], and T. leptospartum [25] account for the strict thermophiles fermenting proteins and peptides, but not amino acids. These microorganisms also use carbohydrates as an energy source. Themanaerobacter themhydrosuljùricus is the only species in the genus Themanaerobacter known to produce H2S from peptide metabolism [l2, 261, and amino acid oxidation has never been demonstrated within this genus. In this paper we fìrst report on the utilization of amino acids by Themzoanaerobacter species and extend the ability to oxidize peptides to other members within this genus, particularly in the presence of thiosulfate. This observation can be regarded as analogous to the situation in which there is growth on amino acids and/or polypeptides in the presence of sulfur by some archaeal hyperthermophiles. Fonds Documentaire ORSTOM C. Faudon et al.: Oxidation by Tlzermoanaerobacter Table 1. Effect of thiosulfate on peptide and amino acid oxidation by SEBR 5268 153 O.D. Acetate Propionate Isobutyrate Isovalerate Treatment 580 nm (mM) b M ) (mh4.l Hz (mM) HzS (mM) M 0.228 6.50 0.00 0.00 0.00 0.00 1.60 MSThio 0.180 6.88 0.00 0.00 0.51 0.00 1.31 Casa 0.209 6.31 0.06 0.14 1.55 5.98 1.82 CasaSThio 0.293 11.87 0.00 1.37 6.28 0.42 6.02 Biot 0.140 5.51 0.42 0.13 1.51 1.45 1.45 BiotSThio 0.323 13.63 0.12 1.93 8.62 0.54 6.88 Pap 0.258 6.60 0.05 0.00 0.48 0.00 1.65 Pan 0.215 6.62 0.23 0.00 0.51 3.84 1.33 Pan+Thio 0.349 11.76 0.37 0.52 2.18 0.43 5.19 Bact 0.160 6.66 0.45 0.00 0.96 6.34 1.66 Bact +Thio 0.330 10.32 0.39 0.45 2.48 0.00 3.9s Biogel 0.180 7.18 0.18 0.00 0.44 7.10 0.56 Biogel+Thio 0.290 13.48 0.14 0.47 2.25 0.00 6.11 Gel 0.200 5.56 0.09 0.00 0.13 1.66 1.90 Gel+Thio 0.260 7.52 0.06 0.00 0.74 0.00 2.27 Results after 3 days of incubation at 60°C. Peptides, casamino acids and gelatin were added at 5 g/liter. M: basal medium containing 1 g/liter yeast extract; Thio: thiosulfate (20m~) ; Casa: casamino acids; Biot: bio-Trypcase; Pap: Soja bean papainic peptone; Pan: pancreatic peptone; Bact: bactopeptone; Biogel: bio-gelytone; Gel: gelatin. Pap +Thio 0.335 11.95 0.15 0.44 2.68 0.00 5.75 Table 2. Effect of thiosulfate on peptide and amino acid oxidation by T. finnii O.D. Acetate Propionate Isobutyrate Isovalerate HZ H zs Treatment (580 nm) (mM) ( n 4 (" (" M 0.113 5.10 0.06 0.00 0.00 0.43 0.96 MtThio 0.116 6.98 0.03 0.00 0.30 0.00 1.08 Casa 0.160 6.08 0.05 0.00 0.70 4.60 1.25 Casa+Thio 0.180 10.29 0.05 1.25 6.43 0.23 5.30 Biot 0.100 6.50 0.06 0.00 0.72 2.76 1.00 Biot+Thio 0.197 9.18 0.09 0.75 5.12 0.94 4.95 Pap 0.110 10.21 0.06 0.00 0.31 6.02 1.01 'I Pap+Thio 0.350 15.20 0.06 0.44 2.82 0.19 8.30 i 4 Pan 0.180 5.46 0.07 0.00 0.11 3.25 1.00 Pan+Thio 0.185 10.02 0.24 0.29 1.70 0.00 2.50 Bact 0.125 6.55 0.45 0.00 0.23 10.17 1.10 Bact+Thio 0.130 8.66 0.40 0.17 1.66 0.19 3.70 Biogel 0.130 6.13 0.07 0.00 0.15 1.27 1.10 Biogel+Thio 0.115 8.36 0.28 0.05 1.14 0.10 1.50 Gel 0.080 5.70 0.06 0.00 0.00 0.79 1.01 Gel+Thio 0.090 6.60 0.07 0.00 0.36 0.00 1.65 Results after 3 days of incubation at 60°C. Peptides, casamino acids and gelatin were added at 5g/liter. M: basal medium containing lg/liter yeast extract; Thio: thiosulfate (20 mM); Casa: casamino acids; Biot: bio-Trypcase; Pap: Soja bean papainic peptone; Pan: pancreatic peptone; Bact: bactopeptone; Biogel: bio-gelytone; Gel: gelatin. I