[Some results of radiaton monitoring of the ISS Russian Segment in 2000-2005].

Dynamics of the ISS RS radiation environment was studied using the data of daily (operative) monitoring and personal dose measurements during 11 increments in the period between August 1, 2000 and October 28, 2005 overlapping the maximum phase of the 23rd solar cycle. It was shown that personal absorbed doses varied within the range of measurements of dual wavelength radiometer R-16, a component of the ISS radiation monitoring system. Power of the absorbed doses fell in the range of 0.017 to 0.02 cGy/day and was solar-dependent.

Iron sequestration on skin: a new route to improved deodorancy.

Axillary malodour is caused by the biotransformation of non-odorous precursors present in apocrine sweat and sebum by the axillary microflora. To counter this, underarm products typically contain high levels of bactericides. However, after an initial decrease in bacterial numbers, the surviving cells grow, producing a concomitant rise in axillary odour. A sustained deodorant effect might be achieved without recourse to bactericidal action if this bacterial growth could be inhibited for extended periods. The current study attempted to inhibit axillary bacterial growth by nutrient deprivation, primarily that of iron (Fe(III)). In vitro analyses identified iron (Fe(III)) as the trace metal whose deprivation had the most profound effect on bacterial growth. Further in vitro investigations with Fe-chelating agents demonstrated that a number of compounds with high binding constants for Fe(III) showed optimal activity. One candidate molecule, diethylenetriaminepentaacetic acid (DTPA), was capable of effectively inhibiting bacterial growth in vitro and on the skin of the lower back. Some bacterial species could additionally utilize iron bound to the iron carrier protein transferrin present in eccrine sweat. This was minimized by the use of an agent, butylated hydroxytoluene (BHT), capable of liberating iron from transferrin via reduction of transferrin-bound ferric ions, allowing subsequent sequestration of Fe(II). Deodorant efficacy evaluation of the combination of DTPA and BHT showed deodorancy benefits over and above that afforded by DTPA alone. This mixture of DTPA and BHT supplemented to a standard ethanolic deodorant, used on 50 people for 2 weeks, was highly effective in limiting bacterial growth in the axilla. Total aerobic bacteria in the axillae were reduced from a mean of log 5.75 (+/-0.73) to log 4.50 (+/-0.90) colony-forming units (cfu) cm(-2) (n = 27, P < 0.01) compared with a non-fortified standard ethanolic deodorant. This was reflected in significant decreases in axillary malodour production, as determined by malodour assessments (P < 0.01). The profile of the axillary microflora was maintained, and all populations were rapidly returned to preuse levels after cessation of product use. This new deodorant technology was benchmarked against leading antimicrobial-based deodorant systems. In three separate deodorant efficacy evaluations, the combination of DTPA and BHT was tested against Triethyl citrate, Triclosan and Farnesol in standard unfragranced ethanolic formulations. The combination of DTPA and BHT showed highly significant deodorancy benefits over and above all these antimicrobial-based deodorant technologies. The combination of an efficient iron chelator with an agent capable of liberating iron from transferrin offers significant benefits in terms of bacterial growth inhibition on the skin and provides a new route to axillary deodorancy.

Interactions between biofilms and the environment.

The surfaces of bacteria are highly interactive with their environment. Whether the bacterium is Gram-negative or Gram-positive, most surfaces are charged at neutral pH because of the ionization of the reactive chemical groups which stud them. Since prokaryotes have a high surface area-to-volume ratio, this can have surprising ramifications. For example, many bacteria can concentrate dilute environmental metals on their surfaces and initiate the development of fine-grained minerals. In natural environments, it is not unusual to find such bacteria closely associated with the minerals which they have helped develop. Bacteria can be free-living (planktonic), but in most natural ecosystems they prefer to grow on interfaces as biofilms; supposedly to take advantage of the nutrient concentrative effect of the interface, although there must also be gained some protective value against predators and toxic agents. Using a Pseudomonas aeruginosa model system, we have determined that lipopolysaccharide is important in the initial attachment of this Gram-negative bacterium to interfaces and that this surface moiety subtly changes during biofilm formation. Using this same model system, we have also discovered that there is a natural tendency for Gram-negative bacteria to concentrate and package periplasmic components into membrane vesicles which bleb-off the surface. Since some of these components (e.g., peptidoglycan hydrolases) can degrade other surrounding cells, the vesicles could be predatory; i.e., a natural system by which neighboring bacteria are targeted and lysed, thereby liberating additional nutrients to the microbial community. This obviously would be of benefit to vesicle-producing bacteria living in biofilms containing mixed microbial populations.

Pseudomonas aeruginosa PAO1 ceases to express serotype-specific lipopolysaccharide at 45 degrees C.

Most Pseudomonas aeruginosa strains are able to produce two distinct lipopolysaccharide (LPS) O-polysaccharide types, A-band (common-antigen) and B-band (serotype-specific) LPSs. The relative expression levels of these two LPS types in P. aeruginosa PAO1 (O5 serotype) at various growth temperatures were investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver staining or Western blotting (immunoblotting) with monoclonal antibodies specific for each O polysaccharide. A-band and B-band LPSs were expressed concurrently when the cells grew at 15, 25, and 35 degrees C; however, growth at 45 degrees C resulted in a surface deficiency in B-band LPS as determined by immunoblotting and agglutination with B-band-specific monoclonal antibody. Transfer of these cells (expressing A-band LPS but deficient in B-band LPS) [A+B-]) to a lower temperature (at which the division time was comparable) resulted in a rapid resumption of normal A-band and B-band expression. B-band LPS was detectable by immunoblotting before measurable growth of the culture had occurred.