The heyday of continuous culture was in the 1960s, when its versatility and reproducibility were used to address fundamental problems in diverse microbiological fields such as biochemistry, ecology, genetics and physiology. The advent of molecular genetics in the 1970s and 1980s led to a decline in the popularity of continuous culture as a standard laboratory tool. The current trend of studying global proteomics, transcriptomics and metabolomics requires reproducible, reliable and biologically homogeneous datasets with which to approach a given problem. The use of continuous culture techniques can aid the acquisition of such data, and continuous cultures offer advantages over biologically heterogeneous batch cultures, where secondary growth and stress effects can often mask subtle physiological differences and trends. This review is intended to remind microbiologists of the value of continuous cultivation in a wide range of biological investigations, and describes some advantages and recent advances in applications of continuous culture in post-genomic studies.

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Trichomonas vaginalis is the etiological agent of trichomoniasis, the most prevalent non-viral sexually transmitted disease worldwide. Trichomoniasis is a widespread, global health concern, and occurring at an increasing rate. Infections of the female genital tract can cause a range of symptoms, including vaginitis and cervicitis, whilst infections in males are generally asymptomatic. The relatively mild symptoms, and lack of evidence for any serious sequelae, have historically led to this disease being under diagnosed, and under researched. However, growing evidence that T. vaginalis infection is associated with disease states with high morbidity in both men and women has increased the efforts to diagnose and treat patients harbouring this parasite. The pathology of trichomoniasis results from damage to the host epithelia, caused by a variety of processes during infection, and recent work has highlighted the complex interactions between the parasite and host, commensal microbiome, and accompanying symbionts. The commercial release of a number of nucleic acid amplification tests (NAATs) has added to the available diagnostic options. Immunoassay based Point of Care testing is currently available, and a recent initial evaluation of a NAAT Point of Care system has given promising results, which would enable testing and treatment in a single visit.

~_ _ _ _ _ _~ _ _ _ _ _ _ _~The production of the pigments actinorhodin and undecylprodigiosin by Stveptomyces coelicolor A3(2) was examined in a chemically defined medium which permits dispersed growth of the organism. The physiological controls on the production of the two pigments were markedly disparate. Actinorhodin production occurred mainly in the stationary phase of batch cultures grown with glucose and sodium nitrate as the principal carbon and nitrogen sources. In the same batch cultures, undecylprodigiosin accumulated during the exponential growth phase. The production of both pigments was sensitive to the levels of ammonium and phosphate in the medium. Actinorhodin production was exquisitely sensitive to ammonium concentration, and was completely inhibited by as little as 1 mM-ammonium chloride, whereas more than 50 mhl-amnonium chloride was required to prevent undecylprodigiosin production. A similar, but less extreme effect was seen with phosphate: actinorhodin production was completely inhibited by 24 mM-phosphate, whereas undecylprodigiosin was still formed at this high phosphate concentration. The effects of ammonium inhibition of pigmented antibiotic production were relieved by reducing the concentration of phosphate in the medium, but changing the ammonium concentration had no effect on phosphate inhibition. Thus the regulation of pigment production by these two nutrients is interrelated, with phosphate control being epistatic to that of ammonium. The results implicate a phosphorylated intermediate as a major regulator of secondary metabolite synthesis by S. coelicolor.