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The microbial dehydrogenation of steroid alkaloids follows the dehydrogenation pattern of steroids until the 3-keto-1,4-diene stage. No side-chain cleavage or degradation of the steroid nucleus is observed. Side-chain cleavage of tomatidine is achieved only by previous induction of side-chain splitting enzymes.
Microbial degradation of pendimethalin (N-(1-Ethylpropyl)-3, 4-dimethyl-2, 6-dinitroaniline) in vitro was studied. Fusarium oxysporum and Paecilomyces varioti, two soil fungi, in culture media degraded pendimethalin to two metabolites namely N-(1-Ethylpropyl)-3, 4-dimethyl-2-nitrobenzene-1, 6-diamine (II) and 3,4-Dimethyl-2, 6-dinitroaniline (IV). Rhizoctonia bataticola, another soil fungus, decomposed pendimethalin yielding only the latter metabolite (IV). Fungal decomposition of pendimethalin involved nitro reduction and dealkylation.
The ecology of hydrocarbon degradation by microbial populations in the natural environment is reviewed, emphasizing the physical, chemical, and biological factors that contribute to the biodegradation of petroleum and individual hydrocarbons. Rates of biodegradation depend greatly on the composition, state, and concentration of the oil or hydrocarbons, with dispersion and emulsification enhancing rates in aquatic systems and absorption by soil particulates being the key feature of terrestrial ecosystems. Temperature and oxygen and nutrient concentrations are important variables in both types of environments. Salinity and pressure may also affect biodegradation rates in some aquatic environments, and moisture and pH may limit biodegradation in soils. Hydrocarbons are degraded primarily by bacteria and fungi. Adaptation by prior exposure of microbial communities to hydrocarbons increases hydrocarbon degradation rates. Adaptation is brought about by selective enrichment of hydrocarbon-utilizing microorganisms and amplification of the pool of hydrocarbon-catabolizing genes. The latter phenomenon can now be monitored through the use of DNA probes. Increases in plasmid frequency may also be associated with genetic adaptation. Seeding to accelerate rates of biodegradation has been shown to be effective in some cases, particularly when used under controlled conditions, such as in fermentors or chemostats.
Microbial degradation of [beta-14C]polystyrene and 1,3-diphenylbutane, a compound structurally representing the smallest repeating unit of styrene (dimer), was investigated in soil and liquid enrichment cultures. Degradation rates in soil, as determined by 14CO2 evolution from applied [14C]polystyrene, varied from 1.5 to 3.0% for a 4-month period. Although relatively low, these percentages were 15 to 30 times greater than values previously reported. Enrichment cultures, containing 1,3-diphenylbutane as the only carbon souce, were used to determine the mechanisms of microbial oxidation of the polymer chain ends. Metabolism of 1,3-diphenylbutane appeared to involve the attack by a monooxygenease to form 2-phenyl-4-hydroxyphenylbutane followed by a further oxidation and subsequent fission of the benzene ring to yield 4-phenylvaleric acid and an unidentified 5-carbon fragment via the classic meta-fission pathway. Phenylacetic acid was probably formed from 4-phenylvaleric acid by subsequent beta-oxidation of the side chain, methyl-oxidation and decarboxylation. An initial examination of the population of microorganisms in the diphenylbutane enrichment cultures indicated that these oxidative reactions are carried out by common soil microorganism of the genera Bacillus, Pseudomonas, Micrococcus, and Nocardia.
Five axenic cultures and a mixed culture were examined for ability to degrade South Louisiana, Brass River Nigerian, Anaco Venezuelan, and Altamont crude oils. A wax was observed during microbial degradation of Altamont crude oil, but not during weathering of the oil. The high-boiling n-alkanes in the wax were associated with microbial degradation of the oil and appeared to be similar to components of tarballs found in the open ocean.
The microbial degradation of a number of 14C-labeled, recalcitrant, aromatic pollutants, including trichloroguaiacol and di-, tri-, and pentachlorophenol, was investigated in aquatic model systems in the laboratory. Natural, mixed cultures of microorganisms in the water from a brown-water lake with a high content of humic compounds mineralized all of the tested substances to a higher degree than did microorganisms in the water from a clear-water lake. Dichlorophenol was the most rapidly degraded pollutant.
The microbial or chemical degradation of lignin from untreated samples of beech wood dusts (Fagus silvatica) resulted in the release of different mutagenic responses in the Salmonella/mammalian plate incorporation assay. In the first experiment using chemical degradation of lignin, dust samples were pre-extracted using acetone-water; the lignin portions were degraded into simpler compounds which were further fractionated on a Sephadex-LH20 column. The compounds isolated from the second phase of Sephadex, representing substances with a 3-4 ring structure and/or those of the same molecular weight, were highly mutagenic towards Salmonella typhimurium TA100 in the presence of metabolic activation. These substances were also active to some extent in strain TA1537 both in the presence and absence of Aroclor-induced rat liver homogenates. In contrast, no direct- or indirect-acting mutagenicity was found when testing with strains TA97 and TA98. Strain TA1535 responded positively only to direct-acting mutagens in the fraction tested. The mutagenic fraction was found to be toxic to the cells when tested in a histidine-rich medium. Repurification of this mutagenic fraction, using silica-gel column chromatography, revealed much higher mutagenic activity than the test material towards strain TA100. In the second pilot experiment, Phanerochaete chrysosporium and Chaetomium globosum, which are known for their ability to degrade lignin, were each incubated with wood dusts in a mixture of physiological saline and nutrient broth for either 3 or 30 days. Significant mutagenic activity was observed with the dust extract after incubation with Ph. chrysosporium but not with Ch. globosum which is a known degrader of beech lignin. These results are discussed regarding hypotheses on the carcinogenicity of beech wood dusts.
Microbial transformation rate constants were determined for seven amides in natural pond water. A second-order mathematical rate expression served as the model for describing the microbial transformation. Also investigated was the relationship between the infrared spectra and the second-order rate constants for these amides. Second-order rate constants (k2) ranged from a low of 2.0 X 10(-14) to a high of 1.1 X 10(-9) liters organism-1 h-1 for niclosamide (2',5-dichloro-4'-nitrosalicylanilide) and propachlor (2-chloro-N-isopropylacetanilide), respectively. The mechanism of degradation (i.e., microbially mediated hydrolysis) of the amides was consistent with that of other organic chemicals previously studied in a variety of natural waters. Preliminary investigations indicate that temporal variations in measured second-order rate constants are small. A simple linear regression of the infrared carbonyl-stretching frequency with log K2 gave a correlation coefficient (r2) of 0.962.
Biodegradation inhibition of a benchmark chemical, 2,4-dichloro-phenoxyacetic acid methyl ester (2,4-DME), was used to quantify the inhibitory effects of heavy metals on aerobic microbial degradation rates of organic chemicals. This procedure used lake sediments and aufwuchs (floating mats) collected in the field or from laboratory microcosms. Effects of CuCl2, HgCl2, ZnCl2, Cd(NO3)2, and Cr(NO3)3 at initial concentrations ranging from 0.3 microM to 73 mM (approximately 0.1 to 10,000 mg liter-1) were investigated. In general, such metallic compounds appeared to be considerably more inhibitory to the biodegradation of an organic chemical than high concentrations of microbially toxic organics studied previously. Effects of various metal concentrations were evaluated based on the following: (i) estimated MICs, (ii) concentrations that caused a significant effect on biodegradation parameters (both a greater than 10% decrease in Vmax and a greater than 10% increase in t1/2 for 2,4-DME degradation), and (iii) concentrations that caused biodegradation half-life doublings (HLDs). The MICs of metals in sediment were lowest for Zn2+ (0.10 microM) and highest for Cd2+ and Cu2+ (0.9 and 1.2 microM, respectively). The MICs of metals in aufwuchs were lowest for Hg2+ (0.01 microM), intermediate for Cu2+ and Zn2+ (0.42 and 0.62 microM, respectively), and highest for Cr3+ and Cd2+ (3.4 and 5.6 microM, respectively). Compared with Cu2+ on aufwuchs, 70 times more Zn2+, 250 times more Cr3+, and 1,000 times more Cd2+ was required to significantly affect aufwuchs biodegradation rate parameters and coefficients (Vmax and t1/2). Aufwuchs was significantly affected by the lowest Hg2+ concentration tested (5 microM).(ABSTRACT TRUNCATED AT 250 WORDS)
The three plant exudates gum traganth, gum arabic, and gum karaya and the two seaweed extracts carrageenan and alginate were degraded by five different Bacilli which were isolated from these gums: Bacillus coagulans, B. lentus, B. cereus, B. licheniformis, and B. firmus. After 14 days all the gums have been degraded by these Bacilli to a different extent after addition of trace elements. The fractions of degraded gums by TLC, GLC, and IR-spectroscopy have been examined with the following results: 1. Except the already known monomers of the above mentioned gums no other monosaccharides could be found. 2. The microbial degradation of gum karaya and alginate resulted in products with a high molecularweight. Monomers could not be determined. 3. Carrageenan has been degraded to oligosaccharides with molecularweights of about 500, 3,6-anhydrogalactose has been partly identified. 4. Gum arabic has been partly degraded to rhamnose and arabinose. 5. Gum traganth has been partly degraded to arabinose and xylose and partly to polysaccharides with molecularweights under 3000.
The extensive use of phosphate-based detergents and agricultural fertilizers is one of the main causes of the world-wide eutrophication of rivers and lakes. To ameliorate such problems partial or total substitution of phosphates in laundry detergents by synthetic, non-phosphorus containing complexing agents is practiced in several countries. The physiological, biochemical and ecological aspects of the microbial degradation of the complexing agents most frequently used, such as polyphosphates, aminopolycarboxylates (especially of nitrilotriacetic acid), and phosphonates are reviewed.
Although various etiologic factors have been implicated, the mechanism responsible for bile acid malabsorption in CF remains unknown. Eight CF children studied twice on a normal diet supplemented with pancreatic enzymes and once during a one-month period of Vivonex administered by continuous nasogastric infusion were compared to age-matched controls. On the fat and residue-free elemental diet, there was a modest decrease in steatorrhea and no change in the daily excretion of nitrogen and neutral sterols. However, normalization of bile acid output (485.6 +/- 65.0 to 160.6 +/- 29.2 mg/24 hr) to control levels (150.2 +/- 60.7) was noted. Diminished microbial degradation of both neutral and acidic sterols and a smaller amount of bile acids adsorbed to decreased residues were also found. The data do not support the possibility of a bile acid ileal transport defect and suggest that the most important single factor responsible for the intraluminal sequestration of bile acids in CF is dietary residues. Because of significant ongoing losses of nitrogen and lipids, pancreatic enzymes should be given to CF patients on elemental diets.
The disappearance of the herbicide, Avadex (40% diallate), from five agricultural soils (differing in either pH, carbon content, or nitrogen content), incubated under sterile and non-sterile conditions, was followed for a period of 20 weeks. Avadex was rapidly lost from microbiologically active soils, with over 50% of the applied (2.5 ppm) dosage disappearing within four weeks; losses from sterile soils were much slower with recoveries of over 50% after 20 weeks. Incubation of soil with Avadex to which 14C-labeled diallate had been added resulted in rapid formation of 14CO2 from microbiologically active samples and only very slow 14CO2 formation from sterile samples. Substantial quantities of radioactivity were retained as unextractable residues in both sterile and non-sterile soils after senven days incubation. From these data it was concluded that the disappearance of the herbicide from non-sterile soils was mainly due to microbial degradation and to binding of diallate or its metabolites as residues to undefined soil components. Losses from sterile soils were attributed to both binding of residues and to a slow chemical degradation. Avadex degradation by pure cultures was studied using representative fungi isolated from the five soils. Of the fungi tested, Phoma eupyrena, Penicillium janthinellum, and Trichoderma harzianium coudl degrade at least 20% of the applied (2.5 ppm) herbicide after ten days incubation. Degradation of Avadex in soil cultures of T. harzianum was found to be slower than degradation in liquid nutrient cultures.
The fate of glycerol trinitrate when exposed to microbial attack has been investigated. Contrary to some earlier reports, this compound was readily biodegraded by employing batch or continuous techniques under a variety of cultural conditions. Breakdown of glycerol trinitrate took place stepwise via the dinitrate and mononitrate isomers, with each succeeding step proceeding at a slower rate. After a residence time of 8 to 15 h, none of the glycerol nitrates could be detected in the effluent from a continuous-culture apparatus (chemostat) supplied with an influent containing 30 mg of glycerol trinitrate per liter.
The possibility that vegetation may be used to actively promote microbial restoration of chemically contaminated soils was tested by using rhizosphere and nonvegetated soils collected from a trichloroethylene (TCE)-contaminated field site. Biomass determinations, disappearance of TCE from the headspace of spiked soil slurries, and mineralization of [14C]TCE to 14CO2 all showed that microbial activity is greater in rhizosphere soils and that TCE degradation occurs faster in the rhizosphere than in the edaphosphere. Thus, vegetation may be an important variable in the biological restoration of surface and near-surface soils.
Cephalothin (CET)-susceptible Escherichia coli, which can degrade CET after prolonged incubation in broth containing a concentration of the drug greater than the minimum inhibitory concentration, was found in a clinical specimen. The substrate specificity of the partially purified enzyme to cephalosporin analogs strongly indicated the occurrence of CET-specific degradation. Nuclear magnetic resonance analysis of the degradation reaction demonstrated the appearance of two new signals attributed to deacetyl CET. This suggests the possibility of the presence of acylesterase.
A total of 40 strains of bacteria were isolated and tested for their potentiality to degrade chitin and utilize shrimp-shell waste for the production of chitinase. The activity ratio, percentage of weight loss and enzyme activity were determined for cultures exhibiting highest chitinolytic activities. The most active organisms were identified as Alcaligenes denitrificans, Bacillus amyloliquefaciens, B. megaterium and B. subtilis. The potentiality of the first two organisms to degrade chitin was reported for the first time.
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