VN November 2020

Vetnews | November 2020 5 On quiet days, we lab rats pursue peculiar hobbies. We make up bucket lists of bacteria we would like to isolate, and some of those listed have unusual colours, making them desirable for artworks. Most bacteria are white or grey, but yellow is common. Staphylococcus aureus lives up to its golden promise. Quite a few are pink or red, such as the intrinsically antibiotic resistant Serratia marcescen s and Rhodococcus equi . Green is rare in the bacterial world, except for Pseudomonas aeruginosa , and quite a few fungi are green, e.g. Aspergillus fumigatus . A bovine sheath wash once yielded a leaf green alga, which happily grew on bacterial agar. Some bacteria produce fluorescent pigments as well or instead of ordinary colours, and a UV lamp can reveal unexpected delights. Pseudomonas aeruginosa produces a variety of fluorescent colours. Selective chromogenic (colour-generating) agars for different bacteria are used in the lab for quick identification. Listeria agar, used during the recent outbreak, shows Listeria as turquoise colonies and all the other bacteria in the sample remain colourless. MacConkey agar, a lab staple, colours E. coli pink and Salmonella yellow. Microbe Art Maryke Henton Various Candida species on a chromogenic agar [ASM] >>> 6