Streptophage-mediated control of off-flavour taint producing streptomycetes isolated from barramundi ponds

Abstract

Off-flavour taint of aquaculture products is a global issue reducing consumer confidence in the farmed produce as they are taken up via the gills of fish, and deposited in the lipids of the animal. If the fish are not purged, resulting undesirable muddy earthy flavour taint can be tasted by consumers. These undesirable flavour and odour is caused by the terpenoid compounds namely geosmin and 2-methylisoborneol, produced as secondary metabolites by certain bacteria including the cyanobacteria and actinomycetes. Current strategies to remediate the problem rely on treating the symptoms not the cause and involve the use of time consuming purging methods and costly chemicals.Biological control using bacteriophages, specific to the problem causing bacteria, offers a natural alternative to chemical control, which might reduce further complications of copper based algaecides and its subsequent implications on water quality. In an adaptation of such biological control approach streptomycetes isolated from barramundi ponds were tested for their susceptibility to streptophages to understand whether host destruction via phage lysis would subsequently eliminate off-flavour taint productions by these isolates.Following the determination of the streptophage susceptibility of the isolates one of the most odourous streptomycete species (USC-14510) was selected to be tested further using different pond simulations resembling real-life applications. Geosmin was tested as the indicator of off-flavour taint production and as it has been previously reported that the cyanobacteria-actinomycete interactions occurring in ponds result in even greater levels of geosmin and 2-methylisoborneol, the geosmin levels for the isolate in the presence of cyanobacteria and streptophages were also tested. Findings indicated that the highly odourous Streptomyces species (USC-14510) once infected with streptophages, can lose its capacity to produce off-flavour taints. Pond simulation studies also revealed geosmin production was significantly reduced when streptophages were introduced into the pond water where streptomycete species were grown. The bacteriophage control method developed in the presented study might again confirm significant potential for the bacteriophage-mediated remediation strategy to be adapted by the aquaculture industry.

Isolation and Characterization of Nocardiae Associated with Foaming Coastal Marine Waters

“…A composite sample of six different phages was prepared using equal volumes of each phages and the phage susceptibility of the isolates was determined using spot test assay as described by Thomas et al [ 8 ]. Lysis zones were evaluated using the index described by Jonns et al [ 69 ].…”

The Fate of Bacteriophages in Recirculating Aquaculture Systems (RAS)—Towards Developing Phage Therapy for RAS

“…For example, geosmin compounds accumulate in fish tissue, causing unwanted earthy taste and odor [27]. Phages infecting geosmin-producing Streptomyces species have already been shown to be capable of reducing geosmin production [28] and could be used in RAS systems to control product quality.…”

Detection and control of off-flavour compound-producing streptomycetes on locally produced nuts using streptophages

“…[3][4][5] Geosmin and 2-MIB are semi-volatile and terpenoid secondary metabolites. 6 Streptomycetes produce these compounds via the 1-deoxy-D-xylulose 5-phosphate/2-C-methyl-D-erythritol 4-phosphate (DOXP/MEP) and melavonic (MVA) pathways. 7 Likewise, dimethyl disulfide is a volatile sulfur compound produced via methionine degradation followed by methanethiol oxidation.…”