The pollution of soil and water with explosives and related compounds caused by military activities has been known for a long time, but progress in understanding the environmental fate of such substances has only been made in the last few years. Microbial processes could be used for the remediation of explosives-contaminated soils and waste waters because it has been shown that a variety of different microorganisms are able to metabolize these chemical compounds. In some cases even a complete mineralization has been found, whereas in others only biotransformation reactions took place, producing more or less toxic and/or recalcitrant metabolites. Studies with pure cultures of bacteria and fungi have given detailed insights into the biodegradation pathways of at least some nitroorganic compounds. Additionally, some of the key enzymes have been isolated and purified or studied in crude extracts. This review summarizes information on the biodegradation and biotransformation pathways of several important explosives. This may be useful in developing microbiological methods for a safe and economic clean-up of soil and water contaminated with such compounds. It also shows the necessity of further investigations concerning the microbial metabolism of these substances.

) ~ EJB 92 1022 N-Formylmethanofuran(CH0-MFR): tetrahydromethanopterin(H4MPT) formyltransferase (formyltransferase) from the extremely thcrmophilic Methanopyrus kandleri was purified over 100-fold to apparent homogeneity with a 54% yield. The monomeric enzyme had an apparent molecular mass of 35 kDa. The N-terminal amino acid sequence of the polypeptide was determined.The formyltransferase was found to be absolutely dependent on the presence of phosphate or sulfate salts for activity. The ability of salts to activate the enzyme decreased in the order K2HP04 > (NH4)2S04 > K2S04 > Na2S04 > Na2HP04. The salts KCI, NaCl and NH4C1 did not activate the enzyme. The dependence of activity on salt concentration showed a sigmoidal curve. For halfmaximal activity, 1 M K2HP04 and 1.2 M (NH4)2S04 were required. A detailed kinetic analysis revealed that phosphates and sulfates both affected the V,,, rather than the K, for CHO-MFR and H4MPT. At the optimal salt concentration and at 6 5 T , the V,,, was 2700 U/mg (1 U = 1 pmol/ min), the K,,, for CHO-MFR was 50 pM and the K, for H4MPT was 100 pM. At 90"C, the temperature optimum of the enzyme, the V,,, was about 2.5-fold higher than at 65 "C.Thermostability as well as activity of formyltransferase was dramatically increased in the presence of salts, 1.5 M being required for optimal stabilization. The efficiency of salts in protecting formyltransrerase from heat inactivation at 90°C decreased in the order K2HP04 = (NH4)2S04 % KC1 = NH4Cl = NaCl % Na,S04 > Na2HP04. The catalytic mechanism of formyltransferase was determined to be of the ternary-complex type. The properties of the enzyme from M. kandleri are compared with those of formyltransferase from Methanobacterium thermoautotrophicunz, Methanosarcina barkeri and Archaeoglohus fulgidus.Metfzanopyrus kandleri is a novel abyssal hyperthermophilic Archaeon, which grows optimally at 98°C on H2 and C 0 2 with the formation of CH4 (Huber et al., 1989;Kurr et al., 1991). The organism, which belongs to the kingdom of Euryarchaeota (Woese et al., 1990), is the most thermophilic mcthanogen known so far and is phylogenetically unrelated to all other methanogens (Burggraf et al., 1991). The pathway of C 0 2 reduction to CH4 has been shown to be identical to that used in all other methanogens (Rospert et al., 1991).M . kundleri grows on a completely mineral salts medium. The concentrations of salts add up to 250 mM (mostly NaCl; Kurr et al., 1991). Despite these relatively low extracellular concentrations, the intracellular concentration of salts in the organism are very high. The predominant solutes found are 2,3-diphosphoglycerate and potassium ions at concentrations above 3 M (Huber et al., 1989>. The high intracellular salt concentrations in M . kundleri are reflected in the properties of two enzymes involved in methanogenesis: N5,N10-mcthenyltetrahydromethanopterin cyclohydrolase (Breitung et a]., 1991) and N5,N1'-methylenetetrahydromethanopterin reductase (Ma et al., 1991a). The catalytic efficiency (kJK,,,) of both enzymes is incre...

Two composting systems were compared on a laboratory scale as a bioremediation technology for degradation or immobilization of 2,4,6-trinitrotoluene (TNT) in contaminated soils. The first compost was aerated from the beginning whereas the second compost was only aerated after an anaerobic prephase of 65 days. In the first compost system the TNT concentration declined rapidly by 92% but, at the end, TNT could be partially recovered. During the anaerobic prephase of the second compost system, TNT was almost completely converted to aminodinitrotoluenes, which during the subsequent aeration almost entirely disappeared. In addition, the second compost generated less toxic material than the first one as confirmed by inhibition of bioluminescence of Vibrio fischeri. These data show that microbiological TNT-degradation systems can be successfully designed which are prerequisite for an efficient bioremediation of contaminated soils.

Formylmethanofuran: tetrahydromethanopterin formyltransferase was purified from methanol grown Methanosarcina barkeri to apparent homogeneity and characterized with respect to its molecular and kinetic properties. The enzyme was found to be very similar to the formyltransferase from H2/CO2 grown :Methanobacterium thermoautotrophicum. It also catalyzed the formation of NS-formyltetrahydromethanopterin rather than of Na°-formyltetrahydromethanopterin from formylmethanofuran and tetrahydromethanopterin, Methanofuran: Formylmethanofuran; Tetrahydromethanopterin; Formyltetrahydromethanopterin: Methanosarcina barkeri;Methanobacteriun~ thermoautotrophit um

The sulfate-reducing Archaeoglobus fulgidus contains a number of enzymes previously thought to be unique for methanogenic Archaea. The purification and properties of two of these enzymes, of formylmethanofuran: tetrahydromethanopterin formyltransferase and of N5,N10-methylenetetrahydromethanopterin dehydrogenase (coenzyme F420 dependent) are described here. A comparison of the N-terminal amino acid sequences and of other molecular properties with those of the respective enzymes from three methanogenic Archaea revealed a high degree of similarity.