Exploring the role of antimicrobials in the selective growth of purple phototrophic bacteria through genome mining and agar spot assays.

Purple non-sulphur bacteria (PNSB) are an emerging group of microbes attractive for applied microbiology applications such as wastewater treatment, plant biostimulants, microbial protein, polyhydroxyalkanoates and H2 production. These photoorganoheterotrophic microbes have the unique ability to grow selectively on organic carbon in anaerobic photobioreactors. This so-called selectivity implies that the microbial community will have a low diversity and a high abundance of a particular PNSB species. Recently, it has been shown that certain PNSB strains can produce antimicrobials, yet it remains unclear whether these contribute to competitive inhibition. This research aimed to understand which type of antimicrobial PNSB produce and identify whether these compounds contribute to their selective growth. Mining 166 publicly-available PNSB genomes using the computational tool BAGEL showed that 59% contained antimicrobial encoding regions, more specifically biosynthetic clusters of bacteriocins and non-ribosomal peptide synthetases. Inter- and intra-species inhibition was observed in agar spot assays for Rhodobacter blasticus EBR2 and Rhodopseudomonas palustris EBE1 with inhibition zones of, respectively, 5.1 and 1.5-5.7 mm. Peptidomic analysis detected a peptide fragment in the supernatant (SVLQLLR) that had a 100% percentage identity match with a known non-ribosomal peptide synthetase with antimicrobial activity.

Haematobium schistosomiasis presenting in the Netherlands as a skin disease.

A rare case is reported of extragenital skin schistosomiasis as the presenting symptom in a 24-year-old Dutch student, who had swum some months earlier in Lake Malawi in Mozambique. Grouped papules dorsolateral on the lower thorax were shown by biopsy to be due to infection by Schistosoma haematobium. The eggs were viable and surrounded by necrosis and partly purulent, partly granulomatous dermatitis that also affected hair follicles. The second biopsy, taken 2.5 months after treatment with praziquantel, still showed viable eggs and necrosis but no more microabscesses. In the third biopsy 5 weeks after a second praziquantel treatment, no eggs were found, but a partly granulomatous abscess forming inflammation affecting a hair follicle was still present.