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A E Konopka

Publications and source records attributed to A E Konopka.

5 recordsLinked to original sources
PubMed2002

Association of microbial community composition and activity with lead, chromium, and hydrocarbon contamination.

Microbial community composition and activity were characterized in soil contaminated with lead (Pb), chromium (Cr), and hydrocarbons. Contaminant levels were very heterogeneous and ranged from 50 to 16,700 mg of total petroleum hydrocarbons (TPH) kg of soil(-1), 3 to 3,300 mg of total Cr kg of soil(-1), and 1 to 17,100 mg of Pb kg of soil(-1). Microbial community compositions were estimated from the patterns of phospholipid fatty acids (PLFA); these were considerably different among the 14 soil samples. Statistical analyses suggested that the variation in PLFA was more correlated with soil hydrocarbons than with the levels of Cr and Pb. The metal sensitivity of the microbial community was determined by extracting bacteria from soil and measuring [(3)H]leucine incorporation as a function of metal concentration. Six soil samples collected in the spring of 1999 had IC(50) values (the heavy metal concentrations giving 50% reduction of microbial activity) of approximately 2.5 mM for CrO(4)2- and 0.01 mM for Pb2+. Much higher levels of Pb were required to inhibit [14C]glucose mineralization directly in soils. In microcosm experiments with these samples, microbial biomass and the ratio of microbial biomass to soil organic C were not correlated with the concentrations of hydrocarbons and heavy metals. However, microbial C respiration in samples with a higher level of hydrocarbons differed from the other soils no matter whether complex organic C (alfalfa) was added or not. The ratios of microbial C respiration to microbial biomass differed significantly among the soil samples (P < 0.05) and were relatively high in soils contaminated with hydrocarbons or heavy metals. Our results suggest that the soil microbial community was predominantly affected by hydrocarbons.

Bacteria↗
PubMed1977

Isolation and characterization of gas vesicles from Microcyclus aquaticus.

Intact gas vesicles of Microcyclus aquaticus S1 were isolated by using centrifugally accelerated flotation of vesicles and molecular sieve chromatography. Isolated gas vesicles were cylindrical organelles with biconical ends and measured 250x100nm. The gas vesicle membrane was composed almost entirely of protein; neither lipid nor carbohydrate was detected, although one mole of phosphate per mole of protein was found. Amino acid analysis indicated that the protein contained 54.6% hydrophobic amino acid residues, lacked sulfur-containing amino acids, and had a low aromatic amino acid content. The protein subunit composition of the vesicles was determined by gel electrophoresis in (i) 0.1% sodium dodecyl sulfate at pH 9.0 and (ii) 5 M urea at pH 2.0. The membrane appeared to consist of one protein subunit of MW 50000 daltons. Charge isomers of this subunit were not detected on urea gels. Antiserum prepared against purified gas vesicles of M. aquaticus S1 crossreacted with the gas vesicles of all other gas vacuolate strains of M. aquaticus, as well as those of Prosthecomicrobium pneumaticum, Nostoc muscorum, and Anabaena flos-aquae, indicating that the gas vesicles of these widely divergent organisms have some antigenic determinants in common.

Amino Acids↗
PubMed1977

Inhibition of gas vesicle production in Microcyclus aquaticus by L-lysine.

The timing and degree of gas vesicle production in Microcyclus aquaticus was affected by nutritional conditions. If 50 microng L-lysine/ml was added to a glucose-mineral salts medium (DM), the organism did not form gas vesicles. This effect was specific for L-lysine, as neither D-lysine nor meso-diaminopimelic acid prevented gas vesicle production. Cells grown in the presence of L-lysine did not contain any immunologically detectable gas vesicle protein, which indicates that L-lysine affects expression of the structural gene for the gas vesicle protein rather than assembly of the protein into gas vesicles. The addition of L-lysine to cultures in DM did not immediately decrease the rate of gas vesicle assembly, nor did the removal of cells from DM plus L-lysine to DM result in immediate gas vesicle production. Gas vesicle production was also affected by the addition of L-threonine or L-cysteine to culture media or by an increase in the medium's ionic strength. These results are discussed in relation to the aspartic acid pathway of amino acid biosynthesis and effects upon the intracellular L-lysine concentration.

Amino Acids↗
PubMed1975

Gas vesicle assembly in Microcyclus aquaticus.

When observed in the electron microscope intact gas vesicles appeared as transparent areas in whole cells of Microcylus aquaticus, whereas vesicles collapsed by centrifugation were not discernible. Within 5 min of suspending cells containing collapsed vesicles in growth medium, small transparent vesicles were detected. By 15 min the average number of vesicles per cell was 15. This number remained relatively constant while the size of the vesicles increased until they attained their maximum diamtere of 100 nm. At this time the vesicles, interpreted as biconical structures, began to elongate presumably due to the synthesis of the cylindrical midsection. Closely correlated with the time at which vesicles began to elongate was the initiation of smaller vesicles which resulted in a doubling of the number of vesicles per cell by 90 min. This evidence coupled with the isolation of a mutant which assembles only the conical portions of the vesicle suggests that assembly occurs in two distinct stages subject to genetic mutation. Protein and ribonucleic acid synthesis, and presumably adenosine triphosphate formation, were required for gas vesicle assembly. In addition, inhibition of protein or ribonucleic acid synthesis resulted in a loss of extant gas vesicles. Over the time course of our study, deoxyribonucleic acid synthesis was not required for gas vesicle assembly or stability.

Bacteria↗