Conventional methods for isolating PNSB have been developed using natural decomposition processes of organic matter such as hay or boiled eggs; or a defined medium containing a single organic compound with a small amount of a mixture of organic growth factors; and source samples directly inoculated into or onto a solid defined medium and incubated under anaerobic light conditions. Such conditions provide for enrichment of PNSB as they can grow and out-compete other microbes (van Niel, 1971).