The large use of conventional plastics has resulted in serious environmental problems. Polyhydroxyalkanoates represent a potent replacement to synthetic plastics because of their biodegradable ...nature. This study aimed to screen bacteria and archaea isolated from an extreme environment, the salt lake Chott El Jerid for the accumulation of these inclusions. Among them, two archaeal strains showed positive results with phenotypic and genotypic methods. Phylogenetic analysis, based on the 16S rRNA gene, indicated that polyhydroxyalkanoate (PHA)-producing archaeal isolates CEJGTEA101 and CEJEA36 were related to
and
, respectively. Gas chromatography and UV-visible spectrophotometric analyses revealed that the PHA were identified as polyhydroxybutyrate and polyhydroxyvalerate, respectively. According to gas chromatography analysis, the strain CEJGTEA101 produced maximum yield of 7 wt % at 37 °C; pH 6.5; 20% NaCl and the strain CEJEA36 produced 3.6 wt % at 37 °C; pH 7; 25% NaCl in a medium supplemented with 2% glucose. Under nutritionally optimal cultivation conditions, polymers were extracted from these strains and were determined by gravimetric analysis yielding PHA production of 35% and 25% of cell dry weight. In conclusion, optimization of PHA production from inexpensive industrial wastes and carbon sources has considerable interest for reducing costs and obtaining high yield.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Polyhydroxyalkanoates (PHAs), green alternatives to petroleum-derived plastics, possess desired features that make them preferred for various applications. Poly(3-hydroxybutyrate) (PHB), one of the ...most known representative of PHAs, could be synthesized by haloarchaeal species but their production amounts are relatively low compared to those of poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) obtained by haloarchaea. This is the first report describing an overproduction of PHB by a wild-type halophilic archaeon isolated from southern Tunisia, Chott El Jerid. According to the 16S rRNA gene sequence analysis, the isolate CEJ40-10 was affiliated with the species of the genus
Haloarcula
(97.5% similarity). Regarding the phylogeny based on the amino acid sequences of the PHA synthase subunits encoded by
phaC
and
phaE
, their identities to those from
Haloarcula quadrata
were 99% and 100%, respectively. This strain could accumulate maximum PHA using 1% (w/v) starch at pH 6, after incubation for 72 h at 37 °C with high salt content (30% NaCl). The replacement of starch with glucose or sugar wastewater lowered the polymer yield. Four extraction methods were performed in order to achieve the maximum efficiency of polymer recovery. Hypochlorite digestion of biomass gave a high recovery yield, reaching 72.8% of its total dry mass. Furthermore, analytical methods such as the Fourier transform infrared (FTIR) spectroscopy, gas chromatography (GC), and UV–visible spectrophotometry indicated that the composition of the polymer was a homopolymer PHB. Our findings showed that
Haloarcula
sp
.
strain CEJ40-10 was a potential PHB-candidate for industrial scale production using starchy substrates.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The screening of bacteria and archaea from Chott El Jerid, a hypersaline lake in the south of Tunisia, led to the isolation of 68 extremely halophilic prokaryotes growing in media with 15–25% of ...salt. Assessment of 68 partial 16S rRNA analyzed by amplified rDNA restriction analysis (ARDRA) revealed 15 different bacterial and archaeal taxonomic groups. Based on ARDRA results, phenotypic and hydrolytic activity tests, 20 archaeal and 6 bacterial isolates were selected for sequencing. The halophilic isolates were identified as members of the genera:
Salicola, Bacillus, Halorubrum, Natrinema
and
Haloterrigena
. Most of these isolates are able to produce hydrolytic enzymes such as amylase, protease, lipase, cellulase, xylanase, pectinase and some of them showed combined activities.
Natrinema
genus is an excellent candidate for lipase production. These results indicated that the extremely halophilic archaea and bacteria from Chott El Jerid are a potential source of hydrolytic enzymes and may possess commercial value.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Probiotics or direct-fed microbials (DFM) have proven strong potential for improving aquaculture sustainability. This study aims to evaluate the effects of dietary supplementation with the DFM
...Bacillus amyloliquefaciens
US573 on growth performance, intestinal morphology, and gut microbiota (GM) of European sea bass. For this purpose, healthy fish were divided into two feeding trials in triplicate of 25 fish in each tank. The fish were fed with a control basal diet or a DFM-supplemented diet for 42 days. Results showed that, while no significant effects on growth performance were observed, the length and abundance of villi were higher in the DFM-fed group. The benefic effects of DFM supplementation included also the absence of cysts formation and the increase in number of goblet cells playing essential role in immune response. Through DNA metabarcoding analysis of GM, 5 phyla and 14 major genera were identified. At day 42, the main microbiome changes in response to
B. amyloliquefaciens
US573 addition included the significant decrease in abundance of Actinobacteria phylum that perfectly correlates with a decrease in
Nocardia
genus representatives which represent serious threat in marine and freshwater fish. On the contrary, an obvious dominance of Betaproteobacteria associated with the abundance in
Variovorax
genus members, known for their ability to metabolize numerous substrates, was recorded. Interestingly, Firmicutes, particularly species affiliated to the genus
Sporosarcina
with recent promising probiotic potential, were identified as the most abundant. These results suggest that
B. amyloliquefaciens
US573 can be effectively recommended as health-promoting DFM in European sea bass farming.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The purpose of the present work is to treat saline Tuna fish wastewater, with the salt concentration of 43 g L
−1
and total organic carbon (TOC) of 8.3 g L
−1
, using an anaerobic fixed bed reactor ...involving salt-tolerant bacteria from the natural hypersaline environment during 150 days. The highest volatile solids (VS) removal efficiency of 84.1% was recorded for the organic loading rate (OLR) of 1.04 g TOC L
−1
.d
−1
and the lowest salinity of 14.6 g NaCl L
−1
. In addition, the maximum biogas production of 0.8 L
−1
.d
−1
for a working volume of 4 L and an organic loading rate of 2.07 g TOC L
−1
.d
−1
correlated with the decrease of Volatile fatty acids (VFA) content. The Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) and the phylogenetic analysis of the bacterial community showed the action of hydrolytic, acidogenic, halotolerant sulfate-reducing and halophilic fermentative bacterium during the processing time. A stable archaeal and methanogenic community's diversity including hydrogenotrophic methanogens was demonstrated with Quantitative-PCR (Q-PCR). The highest bacterial population abundance was detected for 1.45 g TOC L
−1
.d
−1
and the important methanogenic community abundance for 2.07 g TOC L
−1
.d
−1
may be related to the highest biogas production in this charge for an effluent salinity of 27.7 g NaCl L
−1
.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
There is a strong need for long term observations of land surface fluxes such as actual evapotranspiration (ETa). Eddy covariance (EC) method is widely used to provide ETa measurements, and several ...gap-filling methods have been proposed to complete inherent missing data. However, implementing gap-filling methods is questionable for EC time series collected within hilly agricultural areas at the watershed extent. Indeed, changes in wind direction induce changes in airflow inclination and footprint, and therefore possibly induce changes in the relationships on which rely gap-filling methods. This study aimed to obtain continuous ETa time series by adapting gap-filling methods to the particular conditions abovementioned. The experiment took place within an agricultural watershed in north-eastern Tunisia. A 9.6-m-high EC flux tower has been operating close to the watershed center since 2010. The sensible and latent heat fluxes data collected from 2010 to 2013 were quality controlled, and the REddyProc software was used to fill gaps at the hourly timescale. Adapting REddyProc method consisted of splitting the dataset according to wind direction, which improved the flux data at the hourly timescale, but not at the daily and monthly timescales. Finally, complete time series permitted to analyze seasonal and inter-annual variability of ETa.
Halophilic, obligately anaerobic, Gram-stain-negative bacterial strains were isolated from a sediment sample taken from under the salt crust of El-Jerid hypersaline lake in southern Tunisia by using ...tryptone or glucose as the substrate. One strain, CEJFT1B ᵀ, was characterized phenotypically and phylogenetically. Cells were non-motile, non-spore-forming, short rods. Strain CEJFT1B ᵀ was able to grow in the presence of 5–30 % (w/v) NaCl (optimum 20 %) and at 30–60 °C (optimum 45 °C). It grew at pH 5.5–7.8 and the optimum pH for growth was 6.8. The isolate required yeast extract for growth. Substrates utilized by strain CEJFT1B ᵀ as the sole carbon source included glucose, fructose, sucrose, pyruvate, Casamino acids and starch. Individual amino acids such as glutamate, lysine, methionine, serine, tyrosine, and amino acid mixtures formed by the Stickland reaction such as alanine-glycine, valine-proline, leucine-proline, isoleucine-proline were also utilized. Products of glucose fermentation were acetate (major product), butyrate, H ₂ and CO ₂. The genomic DNA G+C content of strain CEJFT1B ᵀ was 32.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain CEJFT1B ᵀ should be assigned to the genus Sporohalobacter . The sequence similarity between strain CEJFT1B ᵀ and Sporohalobacter lortetii was 98.5 %, but DNA–DNA hybridization between the two strains revealed a relatedness value of 56.4 %, indicating that they are not related at the species level. The combination of phylogenetic analysis, DNA–DNA hybridization data, and differences in substrate utilization support the view that strain CEJFT1B ᵀ represents a novel species of the genus Sporohalobacter , for which the name Sporohalobacter salinus sp. nov. is proposed. The type strain is CEJFT1B ᵀ (= DSM 26781 ᵀ = JCM 19279 ᵀ).
Prokaryotic diversity was investigated in a Tunisian salt lake, Chott El Jerid, by quantitative real-time PCR, denaturing gradient gel electrophoresis (DGGE) fingerprinting methods targeting the 16S ...rRNA gene and culture-dependent methods. Two different samples S1-10 and S2-10 were taken from under the salt crust of Chott El Jerid in the dry season. DGGE analysis revealed that bacterial sequences were related to
Firmicutes
,
Proteobacteria
, unclassified bacteria, and
Deinococcus
-
Thermus
phyla. Anaerobic fermentative and sulfate-reducing bacteria were also detected in this ecosystem. Within the domain archaea, all sequences were affiliated to
Euryarchaeota
phylum. Quantitative real-time PCR showed that 16S rRNA gene copy numbers of bacteria was 5 × 10
6
DNA copies g
−1
whereas archaea varied between 5 × 10
5
and 10
6
DNA copies g
−1
in these samples. Eight anaerobic halophilic fermentative bacterial strains were isolated and affiliated with the species
Halanaerobium alcaliphilum
,
Halanaerobium saccharolyticum,
and
Sporohalobacter salinus.
These data showed an abundant and diverse microbial community detected in the hypersaline thalassohaline environment of Chott El Jerid.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Microbial production of bioplastics, derived from poly(3-hydroxybutyrate) (PHB), have provided a promising alternative towards plastic pollution. Compared to other extremophiles, halophilic archaea ...are considered as cell factories for PHB production by using renewable, inexpensive carbon sources, thus decreasing the fermentation cost. This study is aimed at screening 33 halophilic archaea isolated from three enrichment cultures from Tunisian hypersaline lake, Chott El Jerid, using starch as the sole carbon source by Nile Red/Sudan Black staining and further confirmed by PCR amplification of phaC and phaE polymerase genes. 14 isolates have been recognized as positive candidates for PHA production and detected during both seasons. The identification of these strains through 16S rRNA gene analyses showed their affiliation to Halorubrum, Natrinema, and Haloarcula genera. Among them, three PHB-producing strains, CEJ34-14, CEJ5-14, and CEJ48-10, related to Halorubrum chaoviator, Natrinema pallidum, and Haloarcula tradensis were found to be the best ones reaching values of 9.25, 7.11, and 1.42% of cell dry weight (CDW), respectively. Our findings highlighted that Halorubrum, Natrinema, and Haloarcula genera were promising candidates for PHB production using soluble starch as a carbon source under high salinity (250 g L-1 NaCl).
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Chott El Jerid is the largest hypersaline ephemeral lake in southern Tunisian Sahara desert and is one of the biggest depressions at the North of Africa. This study aimed to investigate the diversity ...and abundance of microbial communities inhabiting Chott El Jerid during wet season (when it was flooded), using molecular methods Illumina Miseq sequencing, DGGE and qPCR (qPCR). 16S rRNA gene analyses revealed that bacterial community was dominated by
Proteobacteria
(especially
Ralstonia
species), followed by
Firmicutes
,
Bacteroidetes
,
Cyanobacteria
,
Actinobacteria
and
Verrucomicrobia
. The results obtained using prokaryotic universal primers showed low relative abundance of
Archaea
dominated by few OTUs related to
Methanosarcinaceae
and
Methanomassiliicoccaceae
families and the presence of sulfate-reducing
Archaea
affiliated with
Archaeoglobus
. However, the results obtained using
Archaea
-specific primers showed that archaeal community was mainly composed of aerobic
Halobacteria
(especially
Halorubrum
species) and anaerobic members of
Methanomicrobia
. These results also provided evidence for the presence of members of the genus
Halohasta
in this environment. qPCR results revealed that
Archaea
were more abundant in studied samples than
Bacteria
. The sulfate-reducing
Bacteria
were also found abundant (~ one-third of the bacterial community) and outnumbered methanogens, suggesting their potential important role in this sulfate-rich and hypersaline ecosystem.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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