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 de®cient (UO299). Rhamnolipids produced by PG201 acted to increase the solubility of nhexadecane in the culture medium (from 1Á84 to 22Á76 mg l À1 ). Rates of 14 C-n-hexadecane uptake and mineralization were higher in PG201 than in UO299. However, the degree of difference was lower than expected. Additional studies were carried out on the cell surface properties of the two strains. During growth on n-hexadecane, the cell surface hydrophobicity of both PG201 (50Á5%) and UO299 (33Á7%) increased compared with that observed in water-soluble growth substrates (7±8%). Studies were also carried out to ascertain any energy requirements for the transport of n-hexadecane into Ps. aeruginosa cells. The addition of CCCP (an inhibitor of cytochrome oxidase which thereby blocks oxidative phosphorylation) at a range of concentrations caused a marked decrease in nhexadecane uptake, indicating that n-hexadecane uptake in Ps. aeruginosa is an energydependent process. These studies support the hypothesis of alkane transport into microbial cells by direct contact with larger alkane droplets and by pseudosolubilization. Also, it appears that both mechanisms occur simultaneously.

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. By comparing the 16S rRNA gene sequences, the Pseudomonas sp. discovered was shown to group within the Pseudomonas fluorescens intrageneric cluster. The Serratia isolated was closely related to Serratia plymuthica. Cell growth and degradation was greatest in the Pseudomonas sp. culture where there was breakdown of 60 mg l−1 to 6 mg l−1 technical cypermethrin in 20 days. Tolerance to the SPs was greater in the Pseudomonas sp. but was found to depend on the availability of other carbon sources and nutrients. Conclusions: The bacteria characterized show the potential to be used in a bioremediation application for the treatment of SP residues. Significance and Impact of the Study: The SP‐degrading bacteria may have use in the disposal of used SP residues and with further research could lead to an alternative route of disposal for use in agriculture or industry.

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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; 3á2% and 15á8%, respectively, were positive for Yersinia. Seventy-®ve intestinal samples were taken from house mice from three other farms and 9á3% were positive for Yersinia. The commonest species was Y. enterocolitica (of a wide range of serotypes); all isolates were non-pathogenic, except one of Y. pseudotuberculosis. Salmonella was not isolated from any sample. Conclusions: This study provides additional evidence that house mice are generally not signi®cant vectors of either pathogenic Yersinia strains or Salmonella species. Signi®cance and Impact of the Study: This is the ®rst longitudinal study of Yersinia in any small mammal population, and shows infection to be a dynamic series of generally nonpathogenic, transient infections.

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.