Streptomyces Bacteria as Potential Probiotics in Aquaculture

Abstract

In response to the increased seafood demand from the ever-going human population, aquaculture has become the fastest growing animal food-producing sector. However, the indiscriminate use of antibiotics as a biological control agents for fish pathogens has led to the emergence of antibiotic resistance bacteria. Probiotics are defined as living microbial supplement that exert beneficial effects on hosts as well as improvement of environmental parameters. Probiotics have been proven to be effective in improving the growth, survival and health status of the aquatic livestock. This review aims to highlight the genus Streptomyces can be a good candidate for probiotics in aquaculture. Studies showed that the feed supplemented with Streptomyces could protect fish and shrimp from pathogens as well as increase the growth of the aquatic organisms. Furthermore, the limitations of Streptomyces as probiotics in aquaculture is also highlighted and solutions are discussed to these limitations.

Keywords: Streptomyces; antibiotic resistance; aquaculture; fish pathogens; probiotic.

FIGURE 1

The mechanism of action of probiotic effects of Streptomyces bacteria and their applications in aquaculture. The Streptomyces as probiotic in aquaculture could protect the livestock from pathogens through the production of various antagonistic compounds (e.g., anti-biofilm, anti-quorum sensing and anti-virulence) against Vibrio pathogens. Streptomyces probiotics attenuate the growth of pathogens by producing siderophores which reduce the bioavailability of iron (Fe³⁺) for the pathogens in the aquatic environment. Anti-viral compounds are also produced by Streptomyces probiotic to prevent viral infection caused by white spot syndrome virus (WSSV) in aquaculture. Besides, the Streptomyces probiotics also play a role in ameliorating the water quality of aquaculture. Streptomyces probiotics help to regulate the microflora, especially to increase the protein mineralizing and ammonifying bacterial populations which accelerate the decomposition process of wastes materials and also ameliorate the water quality by reducing the ammonia level (NH₃). The consumption of feeds incorporated with the low pH tolerance and intestinal enzymes resistance Streptomyces probiotics could enhance the growth performance of the livestock by providing good protein sources. Streptomyces probiotics exhibit the ability to secrete hydrolytic exoenzymes which improve the amylolytic and proteolytic activity in the digestive tract of the livestock for more efficient use of the feed; eventually contribute to better growth performance of the livestock.