Environmental microbiology

Role of metal-reducing bacteria in arsenic release from Bengal delta sediments Islam, F. S. et al. Nature 430, 68—71 (2004)

The contamination of groundwater by the release of arsenic from sediments poses a major threat to human health in some parts of Asia, particularly Bangladesh and West Bengal. The mechanisms responsible for this release have been hotly debated. Now, Islam and colleagues report in Nature that their research using a laboratory microcosm approach has provided direct evidence that anaerobic metal-reducing bacteria are involved in the formation of toxic As(III) in sediments collected in West Bengal. They also obtained data to support the theory that the introduction of carbon, for example by irrigation techniques, could be enhancing the mobility of arsenic in shallow groundwater in this area.

Bacterial toxins

A new family of potent AB5 cytotoxins produced by Shiga toxigenic Escherichia coli Paton, A. W. et al. J. Exp. Med. (June 28 2004) doi: 10.1084/jem.20040392

Toxins belonging to the AB5 toxin family are potent virulence factors produced by some bacterial pathogens such as Shiga toxigenic E. coli and Shigella dysenteriae (Shiga toxin), and Bordetella pertussis (pertussis toxin). AB5 toxins comprise an enzymatic A subunit and a pentameric B subunit that is responsible for docking the toxin onto target eukaryotic host cells. In this work, Paton et al. characterize a new member of the AB5 toxin family from a highly virulent Shiga toxigenic E. coli strain. The A subunit of this new toxin has a subtilase-like activity, the first time that a cytotoxic effect has been associated with this serine protease family. The authors speculate that this new toxin could work synergistically with Shiga toxin in the pathogenesis of Shiga toxigenic E. coli.

Environmental microbiology

Molecular analysis of shower curtain biofilm microbes Kelly, S. T. et al. Appl. Environ. Microbiol. 70, 4187—4192 (2004)

When did you last clean your shower curtain? Over time, vinyl shower curtains accumulate a deposit commonly known as soap scum. In a new study published in Applied and Environmental Microbiology, Kelly et al. used a variety of techniques to analyse this material from four shower curtains that had been in use for more than 6 months. Epifluorescence microscopy demonstrated that soap scum contains a rich variety of microorganisms within a biofilm matrix. DNA from the shower curtain communities was extracted and sequenced. rRNA analysis revealed that the composition of each microbial community was complex, with Sphingomonas spp. and Methylobacterium spp. among the most prominent members. The results of this study indicate that shower curtains could be a source of opportunistic pathogens and so should be cleaned regularly, particularly in households with immunosuppressed individuals.