<p>A small number of bacterial pathogens are implicated in urinary tractinfections (UTIs), amongst the most frequent infections in the developedworld. The commonest bacterium isolated from UTI is <taxon tax_id="562">Escherichia coli</taxon>, with streptococcal and staphylococcal species coming a close second [<cite idref="PUB00010405"/>]. Virulent microbes that colonise the human urinary tract usually possess sets ofvirulence factors specific to the host environment [<cite idref="PUB00010405"/>]. The most common are adhesins, molecules that allow an infection to become established; well-characterised E. coli type I pili are a good example.</p><p>Aside from adhesins, other UTI-specific virulence moieties include: toxins, such as Cnf1 and haemolysin, and host biocides that act against othermicrobes competing for the same niche [<cite idref="PUB00010405"/>]. Streptothricin, an antibiotic synthesised and secreted by some Gram-negative pathogens, is an example of the latter [<cite idref="PUB00010405"/>]; the antibiotic also has a toxic effect on host cells. The biocide is synthesised in a five-step process in the bacterial cytoplasm, and secreted to the cell exterior via the general secretory pathway [<cite idref="PUB00010405"/>].</p><p>The last step in the synthesis process is the acetyl co-enzyme A-dependent acetylation of the streptothricin molecule to the mature antibiotic. This is catalysed by the streptothricin acetyltransferase protein, located adjacent to the inner face of the cytoplasmic membrane [<cite idref="PUB00010405"/>]. Homologues of the original gene found in Streptomyces spp. have been found in <taxon tax_id="1423">Bacillus subtilis</taxon> and Staphylococcus spp., as well as E. coli [<cite idref="PUB00010405"/>]. More recently, the streptothricin biosynthesis enzymes were shown to be related to those that carry out non-ribosomal peptide bond formation.</p> Streptothricin acetyltransferase