A study was conducted to determine the role of inoculum size of a bacterium introduced into nonsterile lake water in the biodegradation of a synthetic chemical. The test species was a strain of Pseudomonas cepacia able to grow on and mineralize 10 ng to 30 p,g ofp-nitrophenol (PNP) per ml in salts solution. When introduced into water from Beebe Lake at densities of 330 cells per ml, P. cepacia did not mineralize 1.0 ,ug of PNP per ml. However, PNP was mineralized in lake water inoculated with 3.3 x 104 to 3.6 x 105 P. cepacia cells per ml.
Fluoroquinolone resistance is gradually acquired through several mechanisms. In particular, chromosomal mutations in the genes encoding topoisomerases II and IV and increased expression of the multidrug efflux pump AcrAB-TolC are the most common mechanisms. In this study, multiplex polymerase chain reaction (PCR) protocols were designed for high-throughput sequencing of the quinolone resistance determining regions of topoisomerases genes (gyrA, parC and parE) and/or the expression regulation systems of multidrug efflux pump AcrAB (acrRAB, marRAB and soxSR). These protocols were applied to sequence samples from five subpopulations of 103 clinical Escherichia coli isolates. These subpopulations were classified according to their levofloxacin susceptibility pattern as follows: highly resistant (HR), resistant (R), intermediate (I), reduced susceptibility (RS) and susceptible (S). All HR isolates had mutations in the six genes surveyed, with two ‘supermutator' isolates harboring 13 mutations in these six genes. Strong associations were observed between mutations in acrR and HR isolates, parE and R/HR isolates and parC and I/R/HR isolates, whereas surprisingly, gyrA mutations were common in RS/I/R/HR isolates. Further investigation revealed that strong associations were limited to the triple mutations gyrA-S83L/D87N/R237H and HR isolates and the double mutations S83L/D87N and I/R/HR isolates, whereas the single mutation S83L was common in RS/I/R/HR isolates. Interestingly, two novel mutations (gyrA-R237H and acrR-V29G) were located and found to strongly associate with HR isolates. To the best of our knowledge, the gyrA-R237H and acrR-V29G mutations have never been reported and require further investigation to determine their exact role in resistance or ‘fitness' as defined by their ability to compensate for the organismal cost of gaining resistance.
We examined a total of 150 samples, including 27 eye shadows, 27 mascaras and 96 face creams, for their microbial contents. Mascaras were generally more contaminated than eye shadows. More than 75% of the examined eye shadows contained fewer than 100 c.f.u./g aerobic bacterial count compared to 63% of the mascaras examined. Viable bacteria were not recovered from 61% and 48% of the eye shadows and mascaras respectively. While 4% of the eye shadows were heavily contaminated (contained more than 10(4) c.f.u./g), 15% of the mascaras were as heavily contaminated (with more than 10(4) c.f.u./ml of bacteria). Face creams were generally more heavily contaminated than eye shadows and mascaras. More than 70% of the examined creams contained more than 100 c.f.u./g of bacteria compared to 23% and 37% of eye shadows and mascaras respectively. Only 5% of the face creams were heavily contaminated. However, 27% of the creams were contaminated with more than 10(3)-10(4) c.f.u./g of bacteria compared to none in this range for both eye shadows and mascaras. Qualitative tests for detection of hazardous bacteria showed that none of the eye shadows were contaminated with any of those micro-organisms. Out of nine items of a specific brand of mascara, three isolates of Pseudomonas aeruginosa, one isolate of Citrobacter freundii and one isolate of Klebsiella pneumonia were detected. Among the creams, two brands showed the highest contamination levels with more than 85% of the tested samples containing more than 10(3) c.f.u./g fungi and at least 10(4) c.f.u./g bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)
Aureobasidium pullulans NRRL 6220 synthesized polysaccharide most actively in media containing sucrose, fructose or maltose with (NH4)2SO4 (0.6 g/l) or ammonium acetate giving greatest yields of the polysaccharide. With (NH4)2SO4 at ≥1.2 g/l, production of polysaccharide was decreased considerably. Polysaccharide production was highest with an initial pH of 6.5 while biomass formation was better below an initial pH of 5.5. Optimum phosphate concentration for polysaccharide production was 0.03 M.
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