Mineral and carbon usage of two synthetic pyrethroid degrading bacterial isolates.

Aims: To investigate the biodegrading ability and cometabolism of synthetic pyrethroid (SP) utilizing bacteria in cultures with various minerals and carbon sources.

Methods And Results: Previously isolated SP-degrading Pseudomonas sp. and Serratia sp.

Biodegradation of the synthetic pyrethroid cypermethrin in used sheep dip.

Aims: To investigate the breakdown of cypermethrin synthetic pyrethroid (SP) insecticide-based used sheep dip (USD), with its indigenous microbial community and two previously isolated SP-degrading microorganisms.

Methods And Results: Cultures of USD (50 ml) containing 250 ml l(-1) cypermethrin were inoculated with the SP-degrading organisms and incubated at 25 degrees C with agitation at 80 rev min(-1) for 14 days. The viable cell counts and concentration of cypermethrin were monitored.

Isolation and identification of synthetic pyrethroid-degrading bacteria.

Aims: To isolate, select, identify and assess the potential for the biodegradation of synthetic pyrethroids (SPs) in sheep dips.

Methods And Results: SP-degrading bacteria were isolated from a mixed soil sample consisting of garden soil and soils from farms where SPs had been used. The two largest in size were then identified using microscopy, biochemical and genetic techniques to be members of the genera Pseudomonas and Serratia.

Mechanisms for enhanced biodegradation of petroleum hydrocarbons by a microbe-colonized gas-liquid foam.

Aims: A microbe-colonized gas-liquid foam formulation has been previously shown to provide enhanced biodegradation capabilities in soil microcosms. The present study considers the reservoir properties of this foam and how this affects hydrocarbon degradation rates.

Methods And Results: Oxygen solubility in protein hydrolysate solutions draining from aerated and oxygenated foams was measured.

Patterns of infection by Salmonella and Yersinia spp. in commensal house mouse (Mus musculus domesticus) populations.

Aims: This study sought to examine the risk posed by house mice transmitting pathogens to livestock on typical mixed-agriculture farms in the UK.

Methods And Results: In a 10-month longitudinal study at one farm, 222 faecal samples were taken from mice and 57 swabs from the farm environment; 3.2% and 15.

Role of rhamnolipid biosurfactants in the uptake and mineralization of hexadecane in Pseudomonas aeruginosa.

A study was undertaken to investigate the mechanisms for biosurfactant-enhanced hexadecane uptake into Pseudomonas aeruginosa. Two strains of Ps. aeruginosa were studied, one producing rhamnolipids (PG201) and the other rhamnolipid deficient (UO299).

Effect of protein hydrolysate on the degradation of diesel fuel in soil*.

The addition of protein hydrolysate solution to soil contaminated with diesel fuel was investigated for effects on diesel degradation. The application of protein hydrolysate solution led to an increase in the removal of diesel from the soil. At the end of the 21d experimental period the amount of diesel removed from the soil was 21% greater with the addition of protein hydrolysate solution when compared to a control system.

Bacterial loss from biofilms exposed to free chlorine.

Previous studies have demonstrated the increased resistance of biofilm bacteria to biocides when compared with freely suspended planktonic cells, but there have been few investigations of sloughing and losses from biofilms in response to biocide activity. A model biofilm system was used to demonstrate that the loss of sloughed bacteria (including Escherichia coli as a pathogen indicator organism) from actively growing biofilm reached levels of 10(6)-10(7) CFU ml-1 of eluted medium. The sloughing response was examined in response to a range of free chlorine concentrations from 0.

Evaluation of a dielectrophoretic bacterial counting technique.

Dielectrophoresis, an electrokinetic migration of particles, can occur in non-uniform alternating electric fields and is dependent upon the dielectric nature of the cells and their suspending medium. An enumeration system utilising this phenomenon is described, which has the potential to count particles selectively, including different bacterial or eukaryotic cell species and even sub-populations of different cell viability states or sizes. Relationships were observed between suspension concentrations and the extent of dielectrophoretic (DEP) collection for polystyrene latex beads, pure bacterial samples and mixtures of bacterial species including Escherichia coli, Serratia marcescens, Pseudomonas aeruginosa and Bacillus subtilis.

Dielectrophoretic analysis of microbes in water.

Traditional microbiological methods are still used extensively for analysis of micro-organisms in water. However, they are inefficient due to a high labour input requirement, a low sample capacity, and often a long time lag before results are available. Analytical stages involving incubation and growth (enrichments and colony isolation) contribute the greatest delay in reporting, although subsequent identification can also be protracted.

Analysis of biological particles using dielectrophoresis and impedance measurement.

A novel electrical technique for detecting the collection of particles by dielectrophoresis (DEP) is described. The method is based on the impedance changes resulting from this collection in a microfabricated, integrated dual-channel electrode structure. The results show good agreement with measurements of DEP collection by optical method for suspensions of bacterial species B.

Measurement of the dielectrophoretic enrichment of yeast on grid electrodes using image analysis.

Dielectrophoresis using grid electrode structures offers many advantages for the abstraction and enrichment of cells in analytical microbiology. Modifications to the quantification method of a grid-based dielectrophoresis system are described, utilizing a more rapid and efficient image analysis technique. The grid electrode arrangement enabled dielectrophoretic enrichment of Saccharomyces cerevisiae, resulting in between 36.

Dose-dependent dielectrophoretic response of Cryptosporidium oocysts treated with ozone.

Dielectrophoresis, the motion of particles in non-uniform electric field, was investigated as a technology with the potential for rapid analysis of ozonated Cryptosporidium parvum oocysts. The ratio of dielectrophoretic collection at two key frequencies (100 kHz and 10 MHz) was determined to compare the effect of ozonation at various dosages. A relationship was found between this ratio and the in vitro excystation value obtained at the end of the experiments.

Biodegradation of trace levels of a complex organic pollutant mixture.

Three bacterial isolates with the ability to grow on a model mixture of ground water contaminants were obtained from a sewage works for treatment of industrial effluents, and from heavily and intermediately contaminated ground. The mixture consisted of benzene, toluene, o-xylene, nitrobenzene, 1,4-dichlorobenzene, o-cresol, naphthalene, tetrachloromethane and trichloroethylene, at concentrations ranging from 150 to 600 micrograms/l (2.1 mg/l in total).

Rapid differentiation of untreated, autoclaved and ozone-treated Cryptosporidium parvum oocysts using dielectrophoresis.

A novel automated dielectrophoretic electrode apparatus and procedure was used to differentiate between untreated, autoclaved and ozone treated Cryptosporidium parvum oocysts recovered from water. A freeze-frame video technique enabled images of oocysts to be captured when they collected at sites above and between the electrodes upon application of an electric field. The number of oocysts collecting could then be conveniently counted.

Microbial barrier properties of hen egg shells.

Scanning electron micrographs of shell surfaces revealed a highly fissured outer layer with few open pores on brown eggs but many on white eggs. Total removal of the cuticle with solvents was difficult but partial removal with surface etching was possible using concentrated nitric acid. Staining methods to estimate the number of pores were unsatisfactory but it was possible to detect and count pores on micrographs, as pore mouths were usually associated with depressions and cuticle disruptions.

Degradation of lignin-related compounds by actinomycetes.

Evidence for activity against the lignin fraction of straw was produced for a range of actinomycete strains. Decolorization of the polymeric dye Poly R and oxidation of veratryl alcohol, indicators of ligninolytic activity in white rot fungi, and utilization of fractionated Kraft lignin and low-molecular-weight methoxylated aromatic compounds were the criteria used. The relationships between these activities and the solubilization of native lignin are discussed.

Dimerization of 2,6-dimethoxyphenol by Aspergillus flavus: evidence for the reaction occurring close to mycelia.

Aspergillus flavus grown on 2,6-dimethoxyphenol as sole carbon source produced tetramethoxy-p-dibenzoquinone by a free radical mechanism. The product was identified by H-nmr and ms. Scanning electron microscopy and light microscopy were used to follow the growth of mycelia and the attachment of crystals to the mycelial surfaces.