Study of microbial communities and environmental parameters of seawater collected from three Tunisian fishing harbors in Kerkennah Islands: Statistical analysis of the temporal and spatial dynamics.

Surface seawater, collected from three fishing harbors during different seasons of the years 2015, 2016 and 2017, were assessed for physico-chemical analyses. Results showed that seawater was mainly polluted by hydrocarbons and some heavy metals. Microbial communities' composition and abundance in the studied harbors were performed using molecular approaches. SSCP analysis indicated the presence of Bacteria, Archaea and Eucarya, with dominance of the bacterial domain. Illumina Miseq analysis revealed that the majority of the sequences were affiliated with Bacteria whereas Archaea were detected at low relative abundance. The bacterial community, dominated by Proteobacteria, Bacteroidetes, Planctomycetes, Cyanobacteria, Firmicutes, Actinobacteria and Chloroflexi phyla, are known to be involved in a variety of biodegradation/biotransformation processes including hydrocarbons degradation and heavy metals resistance. The main objectives of this study are to assess, for the first time, the organic/inorganic pollution in surface seawater of Kerkennah Islands harbors, and to explore the potential of next generation marine microbiome monitoring to achieve the planning coastal managing strategies worldwide.

Lipopeptides production by a newly Halomonas venusta strain: Characterization and biotechnological properties.

A halotolerant marine strain PHKT of Halomonas venusta was isolated from contaminated seawater as an efficient biosurfactant producer candidate, on low-value substrate (glycerol). The produced biosurfactants (Bios-PHKT) were characterized as lipopeptides molecules, belonging to surfactin and pumilacidin families, by using Thin Layer Chromatography (TLC), Fourier Transform Infrared Spectroscopy (FT-IR) and Tandem Mass Spectrometry (MALDI-TOF/MS-MS). Bios-PHKT has a critical micelle concentration (CMC) of 125 mg/L, and showed a high steadiness against a wide spectrum of salinity (0-120 g/L NaCl), temperature (4-121 °C) and pH (2-12), supporting its powerful tensioactive properties under various environmental conditions. Likewise, the cytotoxic test revealed that the biosurfactant Bios-PHKT, at concentrations lower than 125 µg/mL, was not cytotoxic for human HEK-293 cells since the cell survival is over than 80%. Furthermore, Bios-PHKT lipopeptides showed excellent anti-adhesive and anti-biofilm activities, being able to avoid and disrupt the biofilm formation by certain pathogenic microorganisms. In addition, the biosurfactant Bios-PHKT showed a remarkable anti-proliferative activity towards tumor B16 melanoma cell line. Besides, Bios-PHKT exhibited an excellent in vitro and in vivo wound healing process. In light of these promising findings, Bios-PHKT could be successfully used in different biotechnological applications.

Investigation of halotolerant marine Staphylococcus sp. CO100, as a promising hydrocarbon-degrading and biosurfactant-producing bacterium, under saline conditions.

A halotolerant strain CO100 of Staphylococcus sp. was isolated from contaminated sediments taken from the fishing harbour of Sfax, Tunisia, as an efficient hydrocarbonoclastic candidate. Strain CO100 exhibited a high capacity to break down almost 72% of the aliphatic hydrocarbons contained in crude oil (1%, v/v), used as the sole carbon and energy source, after 20 days of culture, at 100 g/l NaCl, 37 °C and 180 rpm. The isolate CO100 displayed also its ability to grow on phenanthrene, fluoranthene and pyrene (100 mg/l), at 100 g/l NaCl. Moreover, the isolate CO100 showed a notable aptitude to synthesize an efficient tensioactive agent namely BS-CO100, on low-value substrates including residual frying oil and expired milk powder, thus reducing the high cost of biosurfactant production. The ESI/MS analysis designated that BS-CO100 belonged to lipopeptide class, in particular lichenysin and iturine members. Critical micelle concentrations of BS-CO100 were varying between 65 and 750 mg/l, depending on of the purity of the biosurfactant and the used carbon sources. BS-CO100 showed a high steadiness against a wide spectrum of pH (4.3-12), temperature (4-121 °C) and salinity (0-300 g/l NaCl), supporting its powerful tensioactive properties under various environmental conditions. Likewise, BS-CO100 exhibited no cytotoxic effect toward human HEK293 cells, at concentrations within 125 and 1000 µg/ml. Furthermore, the biosurfactant BS-CO100 exhibited remarkable anti-adhesive and anti-biofilm activities, being able to avoid and disrupt the biofilm formation by certain pathogenic microorganisms. In addition, BS-CO100 was found to have more potential to remove hydrocarbons from contaminated soils, compared to some chemical surfactants. In light of these promising findings, strain CO100, as well as its biosurfactant, could be successfully used in different biotechnological applications including the bioremediation of oil-polluted areas, even under saline conditions.

Isolation and characterization of a newly naphthalene-degrading Halomonas pacifica, strain Cnaph3: biodegradation and biosurfactant production studies.

A newly marine Halomonas pacifica strain Cnaph3 was isolated, as a naphthalene degrader and biosurfactant producer, from contaminated seawater collected in Ataya's fishing harbor, located in Kerkennah Islands, Tunisia. Chromatography flame ionization detector analysis revealed that 98.8% of naphthalene (200 mg/L) was degraded after 7 days of incubation, at 30 g/L NaCl and 37 °C. Strain Cnaph3 showed also a noticeable capacity to grow on a wide range of aliphatic, aromatic, and complex hydrocarbons. Interestingly, strain Cnaph3 showed a significant potential to produce biosurfactants in the presence of all tested substrates, particularly on glycerol (1%, v/v). Electrospray ionization analysis of the biosurfactant, designated Bios-Cnaph3, suggested a lipopeptide composition. The critical micelle concentration of Bios-Cnaph3 was about 500 mg/L. At this concentration, the surface tension of the water was reduced to 27.6 mN/m. Furthermore, Bios-Cnaph3 displayed interesting stabilities over a wide range of temperatures (4-105 °C), salinities (0-100 g/L NaCl), and pH (2.2-12.5). In addition, it showed promising capacities to remove used motor oil from contaminated soils. The biodegradation and biosurfactant-production potential of the Halomonas sp. strain Cnaph3 would present this strain as a favorite agent for bioremediation of hydrocarbon-contaminated sites under saline conditions.