Characterization of culturable bacteria in larval cultures of the Chilean scallop Argopecten purpuratus

Abstract

The early stages of culture of the Chilean scallop Argopecten purpuratus are affected by the mortality attributed to the presence of pathogenic bacteria. The purpose of this study was to characterize the culturable bacteria present in larval cultures of A. purpuratus in the presence and absence of antibiotic (Tetracycline). Bacterial counts on marine agar from water, algal, and larval samples from the culture units were carried out. These counts were performed every three days during 20 days of incubation. The bacterial strains isolated from count plates were identified by 16S rDNA gene sequence analysis. Additionally, the total bacterial counts from culture water were determined by epifluorescence microscopy. Culturable bacterial counts of water samples ranged from 8 × 103 to 3 × 104 CFU mL–1. These counts represent from 3% to 18% of the total bacterial counts. The culturable bacterial counts in larvae were between 3 × 107 and 3 × 108 CFU g–1 and were on average higher in the absence of antibiotic (P < 0.05). Microalgal bacterial counts ranged from 1 × 104 to 9 × 104 CFU mL–1. Of the 46 strains isolated and identified, 25 (54%) belonged to the Gammaproteobacteria, 11 (24%) to the Bacilli, 5 (11%) to the Actinobacteria, 4 (9%) to the Alphaproteobacteria, and 1 (2%) to the Flavobacteria. The most dominant genera in the water samples were Alteromonas, Brevibacterium, Bacillus, Microbacterium, and Marinobacter, while the most dominant genera in larvae were Pseudoalteromonas, Bacillus, Marinobacterium, Alteromonas, and Vibrio, from a total of 15 different bacterial genera identified. The survival of larvae decreased drastically during the 20 days of culture, showing no differences to antimicrobial treatments. The results indicate that there is a high diversity of culturable bacteria present in the larvae, and most are different from those found in the water and microalgae supplied as food.

Effect of florfenicol and oxytetracycline treatments on the intensive larval culture of the Chilean scallopArgopecten purpuratus(Lamarck, 1819)

“…The reason that oxytetracycline treatment was not effective to significantly reduce bacterial content and enhance survival of reared larvae remains unclear, but our results agree with a recent study of Godoy, Espinoza, Wittwer, Uriarte and Aranda (2011) who found that larval survival of smallscale cultures of A. purpuratus in the presence and absence of tetracycline decreased drastically during the 20 days of culture, showing no differences between the treated and untreated cultures.…”

Bacterial Communities in the Water of Larval-Rearing System for the Yesso Scallop (Patinopecten Yessoensis)

“…In addition, Gammaproteobacteria, Alphaproteobacteria and CFB group (Bacteroidetes) have also been detected from seawater in a marine hatchery surrounding waters [18]. Of 12 genera ( Figure 2) described in this study, Pseudoalteromonas and Vibrio have been detected in the water from Great scallop larvae aquaculture systems [2], Alteromonas is one of the dominant genera in the water of Chilean scallop larval-rearing tanks [3], and Glaciecola and Polaribacter are common in the seawater used for the oyster C. gigas hatchery [16]. Vibrio, Alteromonas, Pseudoalteromonas, Shewanella and Marinomonas can be isolated from growing-seawater of Ostrea edulis [19].…”

“…Analyses conducted using Gammaproteobacteria specific probes have also found significant percentages (9%～ 48%) of this bacterial group in total counts of water samples from Chilean scallop larvae culture tanks [17]. A high fraction of the culturable bacteria (60%) are assigned to Gammaproteobacteria, as observed by Godoy et al, in the water of Chilean scallop larvae reared [3]. The bacterial communities in the intake and treated clean seawater from a commercial C. gigas hatchery are dominated by the Alphaproteobacteria, Gammaproteobacteria and Flavobacteria [16].…”

“…As indicated by DGGE, there are high similarities in the bacterial community compositions among different larvae aquaculture systems (stagnant, flow-through and a flow-through system with seawater treated with ozone) [2]. The dominant culturable genera in the water of Chilean scallop Argopecten purpuratus larval rearing tanks and the survival of larvae are different in the presence and absence of antibiotic [3].…”

Microbial characterization of a natural biofilm associated with Peruvian scallop (Argopecten purpuratus) larvae settlement on artificial collector by confocal imaging, microbiology, and metagenomic analysis

“…Moreover, Hoeflea is dominant within the microbiota associated with abalone larvae and their settlement substrate based on NGS analysis (Jiang et al 2017). In contrast, some cultivable Pseudomonas and Marinobacter species are abundantly founded in A. purpuratus larval rearing (Godoy et al 2011).…”