Genome Sequencing and Analysis of Bacillus pumilus ICVB403 Isolated from Acartia tonsa Copepod Eggs Revealed Surfactin and Bacteriocin Production: Insights on Anti-Staphylococcus Activity.

Here we show that Bacillus pumilus ICVB403 recently isolated from copepod eggs is able to produce, after 48-72 h of growth in Landy medium, extracellular inhibitory compounds, which are active against Staphylococcus aureus ATCC 25923, methicillin-resistant S. aureus (MRSA) ATCC 43300, MRSA-S1, Staphylococcus epidermidis 11EMB, Staphylococcus warneri 27EMB, and Staphylococcus hominis 13EMB. Moreover, these extracellular inhibitory compound(s) were able to potentiate erythromycin against the aforementioned staphylococci. The minimum inhibitory concentration (MIC) of erythromycin was reduced from 32 µg/mL to 8 µg/mL for MRSA ATCC 43300 and MRSA SA-1 strains, and from 32-64 µg/mL to 4 µg/mL for S. epidermidis 11EMB and S. hominis 13EMB strains.The genome sequencing and analysis of B. pumilus ICVB403 unveiled 3.666.195 nucleotides contained in 22 contigs with a G + C ratio of 42.0%, 3.826 coding sequences, and 73 RNAs. In silico analysis guided identification of two putative genes coding for synthesis of surfactin A, a lipopeptide with 7 amino acids, and for a circular bacteriocin belonging to the circularin A/uberolysin family, respectively.

Population response of the estuarine copepod Eurytemora affinis to its bioaccumulation of trace metals.

We evaluated the acute toxicities of metals cadmium (Cd), copper (Cu) and nickel (Ni) to a widely-distributed copepod Eurytemora affinis isolated from the Seine estuary. Both sexes of adult E. affinis were exposed separately to the three metals at concentration gradients to determine its 50% lethal concentration (LC50). After 4 days of exposure, both males and females showed a higher sensitivity to Cu (male LC50: 25.0 µg.L-1 and female LC50: 38.0 µg.L-1) than to Ni (male LC50: 90.0 µg.L-1 and female 161.0 µg.L-1) and Cd (male LC50: 127.8 µg.L-1 and female LC50: 90.0 µg.L-1). To assess for the first time, the extend of metal bioaccumulation and its effect at population scale, late stages (>200 µm) were collected and exposed to each metal at the concentration of 1/3 LC50, and to their mixture during 144 h without feeding. The Cd concentration consistently increased with time until the end of the experiment, whereas the Ni and Cu concentrations reached a plateau after 24 h and 72 h exposure, respectively. The results revealed that the copepods could accumulate Cu faster than Ni and Cd either in the treatment alone (0.58 L g-1.d-1) or in the three-metal mixture (0.72 L g-1.d-1) after 50% of exposure time (72 h). The number of individuals decreased in copepod populations except for the Cd treatment, where the number of nauplii increased. In addition, all treatments of metal exposure negatively affected bacterial densities in the copepod cultures, where the Cu treatment showed a negative remarkable effect compared with Cd and Ni treatment did.

Isolation and Characterization of Bacteria Colonizing Acartia tonsa Copepod Eggs and Displaying Antagonist Effects against Vibrio anguillarum, Vibrio alginolyticus and Other Pathogenic Strains.

Copepods represent a major source of food for many aquatic species of commercial interest for aquaculture such as mysis shrimp and early stages of fishes. For the purpose of this study, the culturable mesophilic bacterial flora colonizing Acartia tonsa copepod eggs was isolated and identified. A total of 175 isolates were characterized based on their morphological and biochemical traits. The majority of these isolates (70%) were Gram-negative bacteria. Matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) was used for rapid identification of bacterial isolates. Here, 58% of isolates were successfully identified at the genus level and among them, 54% were identified at the species level. These isolates belong to 12 different genera and 29 species. Five strains, identified as Bacillus pumilus, named 18 COPS, 35A COPS, 35R COPS, 38 COPS, and 40A COPS, showed strong antagonisms against several potential fish pathogens including Vibrio alginolyticus, V. anguillarum, Listeria monocytogenes, and Staphylococcus aureus. Furthermore, using a differential approach, we show that the antimicrobial activity of the 35R COPS strain is linked primarily to the production of antimicrobial compounds of the amicoumacin family, as demonstrated by the specific UV-absorbance and the MS/MS fragmentation patterns of these compounds.