Aims: To isolate and characterize lytic-bacteriophages specific to Microlunatus phosphovorus, and prepare fluorescently labelled phages (FLPs) for the rapid detection of the host bacterium in activated sludge.
Methods and results: Isolation of bacteriophages lytic to M. phosphovorus was attempted by applying supernatants of activated sludge processes on the lawn of M. phosphovorus JCM9379 for plaque formation. Thirteen bacteriophage isolates were obtained. The restriction fragment length polymorphism analysis distinguished them into two different bacteriophages designated as phiMP1 and phiMP2. They were found to possess double-stranded DNA and host specificity. Morphological observations were done by electron microscopy. The bacteriophage particles stained by SYBR Green I was shown to be applicable to detect their host bacterial cells mixed with activated sludge.
Conclusions: Two M. phosphovorus-specific bacteriophages were isolated and classified as Siphoviridae. FLPs of them were prepared, and successfully applied to detect the host bacterium added into the activated sludge.
Significance and impact of the study: At least some of bacteria in activated sludge are susceptible to their related bacteriophages. Bacteriophages lytic to activated sludge bacteria could be affecting the bacterial population in activated sludge. The FLPs could be used for the easy-rapid detection of their host bacterium in activated sludge.