Murine solid tumours as a novel model to study bacterial biofilm formation in vivo.

Bacteria of many species are able to invade and colonize solid tumours in mice. We have focused on Salmonella enterica serovar Typhimurium. Detailed analysis revealed that such tumour-invading Salmonella form biofilms, thus providing a versatile in vivo test system for studying bacterial phenotypes and host-pathogen interactions. It appears that biofilm formation by S. typhimurium is induced as a defence against the immune system of the host, and in particular against neutrophils. Further, we extended our work to the clinically more relevant biofilm infection by Pseudomonas aeruginosa. The induction of P. aeruginosa biofilms in neoplastic tissue appears to be elicited as a reaction against the immune system. Reconstitution experiments reveal that T cells are responsible for biofilm induction. Isogenic mutants that are no longer able to form biofilms can be used for comparison studies to determine antimicrobial resistance, especially therapeutic efficacy against P. aeruginosa located in biofilms.

Towards in vitro potency testing of inactivated erysipelas vaccines.

Ph. Eur. Monograph 0064 "Swine erysipelas vaccine (inactivated)" currently advises mouse serology for batch potency testing. However, technological advances in vaccine production, improved quality control systems and comprehensive post marketing surveillance increasingly promote the acceptance of non-animal approaches for batch release testing. Protein and immune profiles of inactivated swine erysipelas vaccines obtained by SDS-PAGE and Western Blot might offer a convenient global and functional in vitro alternative. Characteristic and consistent protein and immune profiles could be obtained for aluminium-adjuvanted vaccines. Immunoreactivity of polyclonal sera raised in mice differs markedly from reactivity of swine sera.

Effects of elemental sulfur on the metabolism of the deep-sea hyperthermophilic archaeon Thermococcus strain ES-1: characterization of a sulfur-regulated, non-heme iron alcohol dehydrogenase.

The strictly anaerobic archaeon Thermococcus strain ES-1 was recently isolated from near a deep-sea hydrothermal vent. It grows at temperatures up to 91 degrees C by the fermentation of peptides and reduces elemental sulfur (S(o)) to H2S. It is shown here that the growth rates and cell yields of strain ES-1 are dependent upon the concentration of S(o) in the medium, and no growth was observed in the absence of S(o). The activities of various catabolic enzymes in cells grown under conditions of sufficient and limiting S(o) concentrations were investigated. These enzymes included alcohol dehydrogenase (ADH); formate benzyl viologen oxidoreductase; hydrogenase; glutamate dehydrogenase; alanine dehydrogenase; aldehyde ferredoxin (Fd) oxidoreductase; formaldehyde Fd oxidoreductase; and coenzyme A-dependent, Fd-linked oxidoreductases specific for pyruvate, indolepyruvate, 2-ketoglutarate, and 2-ketoisovalerate. Of these, changes were observed only with ADH, formate benzyl viologen oxidoreductase, and hydrogenase, the specific activities of which all dramatically increased in cells grown under S(o) limitation. This was accompanied by increased amounts of H2 and alcohol (ethanol and butanol) from cultures grown with limiting S(o). Such cells were used to purify ADH to electrophoretic homogeneity. ADH is a homotetramer with a subunit M(r) of 46,000 and contains 1 g-atom of Fe per subunit, which, as determined by electron paramagnetic resonance analyses, is present as a mixture of ferrous and ferric forms. No other metals or acid-labile sulfide was detected by colorimetric and elemental analyses. ADH utilized NADP(H) as a cofactor and preferentially catalyzed aldehyde reduction. It is proposed that, under So limitation, ADH reduces to alcohols the aldehydes that are generated by fermentation, thereby serving to dispose of excess reductant.