Assessing the Activity of Antimicrobial Peptides Against Common Marine Bacteria Located in Rotifer (Brachionus plicatilis) Cultures

Abstract

Rotifers are used as the first feed for marine fish larvae and are grown in large cultures that have high loads of organic matter and heterotrophic bacteria; these bacteria are passed on to the developing fish larvae and can potentially lead to bacterial infections. A modified minimum inhibitory concentration (MIC) protocol for antimicrobial peptides was used to determine the potency of ten antimicrobial peptides (AMPs) in artificial seawater relevant to a rotifer culture (salinity of 25‰) against common marine pathogens. All of the AMPs had antimicrobial activity against the bacterial isolates when the salt concentration was approximately zero. However, in high salt concentrations, the majority of the AMPs had an MIC value greater than 65 µg mL−1 in artificial seawater (25‰). The only exceptions were 2009 (32.5 µg mL−1) and 3002 (32.5 µg mL−1) against Vibrio rotiferianus and Tenacibaculum discolor, respectively. The selected synthetic AMPs were not effective at reducing the bacterial load in brackish salt concentrations of a typical commercial rotifer culture (25‰).

Antimicrobial Activity, Genetic Relatedness, and Safety Assessment of Potential Probiotic Lactic Acid Bacteria Isolated from a Rearing Tank of Rotifers (Brachionus plicatilis) Used as Live Feed in Fish Larviculture

“…Rotifers are small-sized live preys, and non-selective filters, that are crucial for delivering essential nutrients and probiotics to underdeveloped fish larvae. Currently, all rotifers are enriched before being supplied to fish larvae, not only to meet nutritional demands, but also to enhance growth, survival rates, and stress tolerance, and promote microbial diversity [19][20][21][22][23][24]. Nevertheless, the rearing tank of rotifer cultures has been recognized as an optimal environment for the growth of pathogenic and opportunistic bacteria, such as Aeromonas spp.…”

“…Hence, strategies to disinfect and clean rotifers of unwanted opportunistic and pathogenic bacteria are a topic of growing interest. However, such strategies have often had a lethal result on the rotifers or yielded inconclusive results [22][23][24]. On the other hand, several authors have previously demonstrated the benefits of enriching rotifers with probiotic bacteria in finfish larviculture systems.…”