Methylation of tin by estuarine microorganisms.

Mixed inoculums of microorganisms from Chesapeake Bay sediments transformed inorganic tin (SnCl(4) . 5H(2)O) to organotin compounds. Dimethyltin and trimethyltin species were identified as products by gas chromatography-mass spectrometry. Methylated tin species were not observed in sterile controls or in poisoned controls. Thus, estuarine microorganisms have the potential for transforming tin to toxic organotins and for mobilizing tin in the ecosystem.

Glyphosate-degrading microorganisms from industrial activated sludge.

A plating medium was developed to isolate N-phosphonomethylglycine (glyphosate)-degrading microorganisms, with glyphosate as the sole phosphorus source. Two industrial biosystems treating glyphosate wastes contained elevated microbial counts on the medium. One purified isolate metabolized glyphosate to aminomethylphosphonic acid, mineralizing this accumulating intermediate during log growth. This microorganism has been identified as a Flavobacterium species.

Tin and tin-resistant microorganisms in chesapeake bay.

Sediment and water samples from nine stations in Chesapeake Bay were examined for tin content and for microbial populations resistant to inorganic tin (75 mg of Sn liter as SnCl(4).5H(2)O) or to the organotin compound dimethyltin chloride [15 mg of Sn liter as (CH(3))(2)SnCl(2)]. Tin concentrations in sediments were higher (3.0 to 7.9 mg kg) at sites impacted by human activity than at open water sites (0.8 to 0.9 mg kg), and they were very high (239.6 mg kg) in Baltimore Harbor, which is impacted by both shipping and heavy industry. Inorganic tin (75 mg Sn liter) in agar medium significantly decreased viable counts, but its toxicity was markedly reduced in liquid medium; it was not toxic in medium solidified with silica gel. Addition of SnCl(4).5H(2)O to these media produced a tin precipitate which was not involved in the metal's toxicity. The data suggest that a soluble tin-agar complex which is toxic to cells is formed in agar medium. Thus, the toxicity of tin depends more on the chemical species than on the metal concentration in the medium. All sites in Chesapeake Bay contained organisms resistant to tin. The microbial flora was more sensitive to (CH(3))(2)SnCl(2) than to SnCl(4).5H(2)O. The elevated level of tin-resistant microorganisms in some aeas not containing unusually high tin concentrations suggests that factors other than tin may participate in the selection for a tin-tolerant microbial flora.

Microbial transformation of nitroaromatic compounds in sewage effluent.

The transformation of mono- and dinitroaromatic compounds was measured in sewage effluent maintained under aerobic or anaerobic conditions. Most of the nitrobenzene, 3- and 4-nitrobenzoic acids, and 3- and 4-nitrotoluenes and much of the 1,2- and 1,3-dinitrobenzenes disappeared both in the presence and absence of oxygen. Under anaerobiosis, 2,6-dinitrotoluene and 3,5-dinitrobenzoic acid disappeared slowly, but no loss was evident in 28 days in aerated sewage. Aromatic amines did not accumulate during the aerobic decomposition of the mononitro compounds. They did appear in nonsterile, but not in sterile, sewage incubated aerobically with the dinitro compounds and anaerobically with all the chemicals. Analysis by gas chromatography and combined gas chromatography-mass spectrometry showed that aniline was formed from nitrobenzene, toluidine was formed from 3- and 4-nitrotoluenes, and aminobenzoic acid was formed from 3- and 4-nitrobenzoic acids under anaerobiosis, and that nitroaniline was formed from 1,2- and 1,3-dinitrobenzenes, aminonitrotoluene resulted from 2,6-dinitrotoluene, and aminonitrobenzoic acid was a product of 3,5-dinitrobenzoic acid under both conditions. The isomeric forms of the metabolites were not established. Aniline, 4-toluidine, and 4-aminobenzoic acid added to sewage disappeared from aerated nonsterile, but not from sterile, sewage or sewage in the absence of oxygen. 2-Nitroaniline, 2-amino-3-nitrotoluene, and 2-amino-5-nitrobenzoic acid added to sewage persisted for at least 60 days in aerobic or anaerobic conditions. Gas chromatographic and gas chromatographic-mass spectrometric analyses demonstrated that acetanilide and 2-methylquinoline were formed from aniline, 4-methylformanilide and 4-methylacetanilide were formed from 4-toluidine, 2-methylbenzimidazole was a product of 2-nitroaniline, and unidentified benzimidazoles were formed from 2-amino-3-nitrotoluene in the absence of oxygen, and that 2-nitroacetanilide and 2-methyl-6-nitroacetanilide were formed from 2-nitroaniline and 2-amino-3-nitrotoluene, respectively, in the presence or absence of oxygen. It is suggested that the transformations of widely used nitroaromatic compounds should be further studied because of the persistence and possible toxicity of products of their metabolism.

The growth of Mycobacterium convolutum on solid n-alkane substrates: effect on cellular lipid composition.

Growth rates and cell yields of Mycobacterium convolutum strain R22 grown on a wide range of both odd- and even-numbered carbon solid n-alkanes decreased as the substrate carbon number increased. Cellular lipid was 2.5 times higher following growth on the hydrocarbon substrates. The amount of polar lipid was found to be about half of the cellular lipid in docosane through octacosane-grown cells. Phosphatidylethanolamine represented about 50% of the polar phospholipid in hydrocarbon- and nonhydrocarbon-grown cells. Phosphatidylserine, diphosphatidylglycerol, and phosphatidic acid were also found. The amount of phosphatidylserine was higher (10-14%) in docosane through octacosane-grown cells. There was a correspondingly smaller amount of diphosphatidylglycerol. These lipid changes may be associated with the assimilation of the hydrophobic substrates. The failure to detect label in lipids of solid n-alkane-grown cells incubated in the presence of [14C]acetate suggested that de novo synthesis of fatty acids did not occur to an appreciable extent. Transport of [14C]acetate and incorporation into cellular protein was not inhibited. Polar lipid fatty acid analyses indicated there was no direct incorporation of the oxidized substrate. The results suggest that beta-oxidation and a subterminal oxidative cleavage appear to be the major catabolic routes providing fatty acids, which are then incorporated into lipid.

Glyphosate degradation by immobilized bacteria: laboratory studies showing feasibility for glyphosate removal from waste water.

To evaluate immobilized bacteria technology for the removal of low levels of glyphosate (N-phosphonomethylglycine) from aqueous industrial effluents, microorganisms with glyphosate-degrading activity obtained from a fill and draw enrichment reactor inoculated with activated sludge were first exposed to glyphosate production wastes containing 500-2000 mg glyphosate/L. The microorganisms were then immobilized by adsorption onto a diatomaceous earth biocarrier contained in upflow Plexiglas columns. The columns were aerated, maintained at pH 7.0-8.0, incubated at 25 degrees C, supplemented with NH4NO3 (50 mg/L), and exposed to glyphosate process wastes pumped upflow through the biocarrier. Glyphosate degradation to aminomethylphosphonic acid was initially > 96% for 21 days of operation at flows yielding hydraulic residence times (HRTs) as short as 42 min. Higher flow rate studies showed > 98% removal of 50 mg glyphosate/L from the waste stream could be achieved at a HRT of 23 min. Glyphosate removal of > 99% at a 37-min HRT was achieved under similar conditions with a column inoculated with a pure culture of Pseudomonas sp. strain LBr, a bacterium known to have high glyphosate-degrading activity. After acid shocking (pH 2.8 for 18 h) of a column of immobilized bacteria, glyphosate-degrading activity was regained within 4 days without reinoculation. Although microbial growth and glyphosate degradation were not maintained under low organic nutrient conditions in the laboratory, the low levels of degradable carbon (45-94 mg/L) in the industrial effluent were sufficient to support prolonged glyphosate-degrading activity. The results demonstrated that immobilized bacteria technology is effective in removing low levels of glyphosate in high-volume liquid waste streams.

Glyphosate degradation by immobilized bacteria: field studies with industrial wastewater effluent.

Immobilized bacteria have been shown in the laboratory to effectively remove glyphosate from wastewater effluent discharged from an activated sludge treatment system. Bacterial consortia in lab columns maintained a 99% glyphosate-degrading activity (GDA) at a hydraulic residence time of less than 20 min. In this study, a pilot plant (capacity, 45 liters/min) was used for a field demonstration. Initially, activated sludge was enriched for microbes with GDA during a 3-week biocarrier activation period. Wastewater effluent was then spiked with glyphosate and NH4Cl and recycled through the pilot plant column during start-up. Microbes with GDA were enhanced by maintaining the pH at less than 8 and adding yeast extract (less than 10 mg/liter). Once the consortia were stabilized, the column capacity for glyphosate removal was determined in a 60-day continuous-flow study. Waste containing 50 mg of glyphosate per liter was pumped at increasing flow rates until a steady state was reached. A microbial GDA of greater than 90% was achieved at a 10-min hydraulic residence time (144 hydraulic turnovers per day). Additional studies showed that microbes with GDA were recoverable within (i) 5 days of an acid shock and (ii) 3 days after a 21-day dormancy (low-flow, low-maintenance) mode. These results suggest that full-scale use of immobilized bacteria can be a cost-effective and dependable technique for the biotreatment of industrial wastewater.

Biodegradation of N-phosphonomethyliminodiacetic acid by microorganisms from industrial activated sludge.

A microbial population that biodegraded N-phosphonomethyliminodiacetic acid (PIA), a key component of glyphosate (N-phosphonomethylglycine) process waste, was established. The stoichiometric conversion of PIA to aminomethylphosphonic acid (AMPA) was observed in a laboratory sequencing batch reactor (SBR) containing activated sludge from a glyphosate-manufacturing facility and PIA as sole source of carbon. PIA degradation was determined by high-performance liquid chromatography and confirmed by radiolabeled studies. Greater than 90% of the [carboxymethyl-2-14C]-label of PIA was released as 14CO2 in 7 days using samples of sludge from the SBR. The cycle time required to biodegrade up to 7.5 mM PIA in SBRs was reduced from 21 to < 3 days. PIA biodegradation was also established in an immobilized bacteria column inoculated with mixed liquor from a SBR; > 99% PIA removal was achieved at an influent concentration of 2.2 mM and a hydraulic retention time of < 10 h. A pure bacterial culture was isolated from a SBR by streaking samples of sludge on solid media with PIA as sole carbon source. The isolate was identified as Xanthomonas maltophilia. In liquid culture, X. maltophilia degraded up to 4.4 mM PIA within 10 days and produced stoichiometric amounts of AMPA. The results demonstrate the biodegradation of PIA and suggest the potential for its treatment in industrial biological treatment systems.

Factors affecting the toxic effect of tin on estuarine microorganisms.

Inorganic tin (SnCl(4).H(2)O) is toxic to microbial populations obtained from estuarine sediments plated on nutrient medium solidified with either agar or purified agar. The use of gelatin as a gelling agent decreased the apparent toxicity of tin, and toxicity was markedly reduced in medium solidified with silica gel. There was no evidence that toxic agar-tin complexes were involved. Cd, Cu, Pb, Ni, and Zn exhibited similar toxicity patterns; therefore, toxicity levels determined in the laboratory should be extrapolated to the environment with caution. The addition of cysteine to the medium had no effect on tin toxicity. Serine or 3-hydroxyflavone enhanced toxicity, while humic acids or gelatin inhibited toxicity. Replacement of SO(4) with NO(3) did not alter tin toxicity, but replacement of Cl with NO(3) decreased tin toxicity. Thus, the toxic effect(s) of tin depend as much on the chemical speciation of the metal as on the total concentration of the metal in the medium.

Metabolism of glyphosate in Pseudomonas sp. strain LBr.

Metabolism of glyphosate (N-phosphonomethylglycine) by Pseudomonas sp. strain LBr, a bacterium isolated from a glyphosate process waste stream, was examined by a combination of solid-state 13C nuclear magnetic resonance experiments and analysis of the phosphonate composition of the growth medium. Pseudomonas sp. strain LBr was capable of eliminating 20 mM glyphosate from the growth medium, an amount approximately 20-fold greater than that reported for any other microorganism to date. The bacterium degraded high levels of glyphosate, primarily by converting it to aminomethylphosphonate, followed by release into the growth medium. Only a small amount of aminomethylphosphonate (about 0.5 to 0.7 mM), which is needed to supply phosphorus for growth, could be metabolized by the microorganism. Solid-state 13C nuclear magnetic resonance analysis of strain LBr grown on 1 mM [2-13C,15N]glyphosate showed that about 5% of the glyphosate was degraded by a separate pathway involving breakdown of glyphosate to glycine, a pathway first observed in Pseudomonas sp. strain PG2982. Thus, Pseudomonas sp. strain LBr appears to possess two distinct routes for glyphosate detoxification.