The effects of benzo[a]pyrene on the composition of gut microbiota and the gut health of the juvenile sea cucumber Apostichopus japonicus Selenka.

The gut microbiota is essential for health and physiological functions in the host organism. However, the toxicological evaluation of environmental pollutants on the gut microbiota is still insufficient. In the present study, the juvenile sea cucumber Apostichopus japonicus was exposed for 14 days to Benzo[a]pyrene (BaP), which is a model polycyclic aromatic hydrocarbon (PAH), at four different concentrations (0, 0.5, 5, and 25 µg/L). We analyzed the intestinal microbial community of A. japonicas using 16S rRNA gene amplicon sequencing. Our results demonstrate that BaP exposure caused alterations to the microbiome community composition in sea cucumbers. At the phylum level, Planctomycetes were significantly more abundant in BaP exposure groups at 14 d compared with the control group, and the abundance of Proteobacteria and Bacteroidetes increased while the abundance of Firmicutes decreased following BaP exposure. At the genus level, multiple beneficial and autochthonous genera declined in the BaP treatment groups compared to the control, including Lactococcus, Bacillus, Lactobacillus, Enterococcus, Leuconostoc and Weissella; however, a bloom of alkane-degrading bacteria was found in BaP-exposed guts and included Lutibacter, Pseudoalteromonas, Polaribacter, Rhodopirellula and Blastopirellula. Furthermore, histological morphology, enzymatic activity and gene expression analysis revealed that BaP exposure also negatively impacted gut structure and function and presented as inflammation or atrophy, oxidative stress and immune suppression in sea cucumber intestines. Collectively, these findings provide insights into the toxic effects of BaP exposure on A. japonicas associated with intestinal microbiota and health.

Effects of terminal electron acceptors on the biodegradation of waste motor oil using Chlorella vulgaris-Rhodococcus erythropolis consortia: Kinetic and thermodynamic windows of opportunity analysis.

The Chlorella vulgaris-Rhodococcus erythropolis consortia was constructed for the biodegradation of waste motor oil (WMO), combined with thermodynamic calculations and stoichiometric analyses. The microalgae-bacteria consortium was constructed as C. vulgaris: R. erythropolis = 1:1 (biomass, cell/mL), pH = 7, 3 g/L WMO. Under the same condition, the terminal electron acceptors (TEAs) play a crucial role in the WMO biodegradation, which follows Fe3+ >SO42- > none. The biodegradation of WMO fitted well with the first-order kinetic model under experimental temperatures with different TEAs (R2 >0.98). The WMO biodegradation efficiency reached 99.2 % and 97.1 % with Fe3+ and SO42-as TEAs at 37 °C, respectively. Thermodynamic methanogenesis opportunity windows with Fe3+ as TEA are 2.72 times fold as large as those with SO42-. Microorganism metabolism equations demonstrated the viability of anabolism and catabolism on WMO. This work lays the groundwork for the implementation of WMO wastewater bioremediation and supports research into the biochemical process of WMO biotransformation.

Sulfide causes histological damage, oxidative stress, metabolic disorders and gut microbiota dysbiosis in juvenile sea cucumber Apostichopus japonicus Selenka.

Sulfide is a common harmful substance in sediments, with an especially high risk for deposit feeder organisms. The sea cucumber Apostichopus japonicus is a typical benthic feeder, and its intestine is the first line of defense and serves as a crucial barrier function. In this study, histological, physiological, gut microbiota, and metabolomic analyses were performed to explore the toxic response in the intestine of juvenile A. japonicus exposed to 0, 0.8, and 1.6 mg/L sulfide stress for 96 h. The results revealed sulfide-induced intestinal inflammatory symptoms and oxidative stress. Moreover, gut bacterial composition was observed after sulfide exposure, with an increase in Proteobacteria and a decrease in Cyanobacteria and Planctomycetes. Specifically, sulfide increased a set of sulfide-removing bacteria and opportunistic pathogens while decreasing several putative beneficial substance-producing bacteria. The metabolomic analysis indicated that sulfide also disturbed metabolic homeostasis, especially lipid and energy metabolism, in intestine. Interestingly, several intestinal bacteria were further identified to be significantly correlated with metabolic changes; for example, the decreased abundance levels of Bacillus, Corynebacterium, and Psychromonas were positively correlated with important energy metabolites, including maleic acid, farnesyl pyrophosphate, thiamine, butynoic acid, and deoxycholic acid. Thus, our research provides new insights into the mechanisms associated with the intestinal metabolic and microbiota response involved in sulfide stress adaptation strategies of juvenile A. japonicus.

The effective removal of Congo Red using a bio-nanocluster: Fe3O4 nanoclusters modified bacteria.

A bio-nanocluster (Fe3O4@bacteria) was prepared by simply mixture using the bacterial suspension and Fe3O4 nanoclusters to remove Congo red (CR) contamination from water resources. The bio-nanocluster was characterized by SEM, TEM and XPS. Adsorption efficiency, adsorption process and adsorption mechanism were comprehensively investigated. The maximum adsorption capacity (Qm) of CR dye onto the Fe3O4@bacteria peaked at 320.1 mg/g, which was 2.88 times that of Fe3O4 under the same condition. Based on the equilibrium and kinetic studies, the Langmuir isotherm theory and pseudo-first-order model is appropriate to describe the adsorption process. The adsorption of CR is spontaneous and exothermic according to the thermodynamics parameters (ΔGθ, ΔHθ and ΔSθ). The adsorption force dominated the Van der Waals force, biofloculation and chemisorption. The Fe3O4@bacteria could be applied potentially as an absorbent with high efficiency and environmentally friendly remediation of dyeing wastewater.

Microbial degradation of four crude oil by biosurfactant producing strain Rhodococcus sp.

Rhodococcus erythropolis M-25, one of the representative biosurfactant producers, performed effectively during the biodegradation of four crude oil. The microbial degradation efficiency is positively relevant to the API of the crude oil. The chemical dispersant Corexit 9500A did not enhance the biodegradation of the petroleum hydrocarbons during the experimental period. 70.7% of the N-4 oil was degraded after 30days, while in the Corexit 9500A plus sample the biodegradation removal was 42.8%. The Corexit-derived compounds were metabolized by M-25 at the same time of the petroleum hydrocarbons biodegrading. Neither biodegradation nor chemical dispersion process has almost no effect on the biomarker (m/z=231). The saturated methyl-branched fatty acids increased from 37.3%, to 49.4%, when M-25 was exposed with the N-4 crude oil. Similarly, the saturated methyl-branched fatty acids in the membrane of N3-2P increased from 20.25% to 44.1%, when exposed it with the N-4 crude oil.

Biodegradation of different petroleum hydrocarbons by free and immobilized microbial consortia.

The efficiencies of free and immobilized microbial consortia in the degradation of different types of petroleum hydrocarbons were investigated. In this study, the biodegradation rates of naphthalene, phenanthrene, pyrene and crude oil reached about 80%, 30%, 56% and 48% under the optimum environmental conditions of free microbial consortia after 7 d. We evaluated five unique co-metabolic substances with petroleum hydrocarbons, α-lactose was the best co-metabolic substance among glucose, α-lactose, soluble starch, yeast powder and urea. The orthogonal biodegradation analysis results showed that semi-coke was the best immobilized carrier followed by walnut shell and activated carbon. Meanwhile, the significance of various factors that contribute to the biodegradation of semi-coke immobilized microbial consortia followed the order of: α-lactose > semi-coke > sodium alginate > CaCl2. Moreover, the degradation rate of the immobilized microbial consortium (47%) was higher than that of a free microbial consortium (26%) under environmental conditions such as the crude oil concentration of 3 g L(-1), NaCl concentration of 20 g L(-1), pH at 7.2-7.4 and temperature of 25 °C after 5 d. SEM and FTIR analyses revealed that the structure of semi-coke became more porous and easily adhered to the microbial consortium; the functional groups (e.g., hydroxy and phosphate) were identified in the microbial consortium and were changed by immobilization. This study demonstrated that the ability of microbial adaptation to the environment can be improved by immobilization which expands the application fields of microbial remediation.

Effect of rhamnolipid biosurfactant on solubilization of polycyclic aromatic hydrocarbons.

Rhamnolipid biosurfactant-producing bacteria, Bacillus Lz-2, was isolated from oil polluted water collected from Dongying Shengli oilfield, China. The factors that influence PAH solubilization such as biosurfactant concentration, pH, ionic strength and temperature were discussed. The results showed that the solubilities of naphthalene, phenanthrene and pyrene increased linearly with the rise of rhamnolipid biosurfactant dose above the biosurfactant critical micelle concentration (CMC). Furthermore, the molar solubilization ratio (MSR) values decreased in the following order: naphthalene>phenanthrene>pyrene. However, the solubility percentage increased and followed the opposite order: pyrene>phenanthrene>naphthalene. The solubilities of PAHs in rhamnolipid biosurfactant solution increased with the rise of pH and ionic strength, and reached the maximum values under the conditions of pH11 and NaCl concentration 8 g · L(-1). The solubility of phenanthrene and pyrene increased with the rise of temperature.

Bioremediation of the oil spill polluted marine intertidal zone and its toxicity effect on microalgae.

Custom-designed devices with 0.6 m (L) × 0.3 m (W) × 0.4 m (H) and a microbial consortium were applied to simulate bioremediation on the oil spill polluted marine intertidal zone. After the bioremediation, the removal efficiency of n-alkanes and polycyclic aromatic hydrocarbon homologues in crude oil evaluated by GC-MS were higher than 58% and 41% respectively. Besides, the acute toxicity effects of crude oil on three microalgae, i.e. Dicrateria sp., Skeletonema costatum and Phaeodactylum tricornutum, varied with concentration. The effects of microbe and surfactant treated water on the three microalgae followed a decreasing order: the microbial consortium plus Tween-80 > the microbial consortium > Tween-80. During 96 h, the cell densities of the three microalgae in treated seawater increased from 4.0 × 10(5), 1.0 × 10(5) and 2.5 × 10(5) cells per mL to 1.7 × 10(6), 8.5 × 10(5) and 2.5 × 10(6) cells per mL, respectively, which illustrated that the quality of seawater contaminated by crude oil was significantly improved by the bioremediation.

Lipopeptide biosurfactant production bacteria Acinetobacter sp. D3-2 and its biodegradation of crude oil.

In this work, a hydrocarbon-degrading bacterium D3-2 isolated from petroleum contaminated soil samples was investigated for its potential effect in biodegradation of crude oil. The strain was identified as Acinetobacter sp. D3-2 based on morphological, biochemical and phylogenetic analysis. The optimum environmental conditions for growth of the bacteria were determined to be pH 8.0, with a NaCl concentration of 3.0% (w/v) at 30 °C. Acinetobacter sp. D3-2 could utilize various hydrocarbon substrates as the sole carbon and energy source. From this study, we also found that the strain had the ability to produce biosurfactant, with the production of 0.52 g L(-1). The surface tension of the culture broth was decreased from 48.02 to 26.30 mN m(-1). The biosurfactant was determined to contain lipopeptide compounds based on laboratory analyses. By carrying out a crude oil degradation assay in an Erlenmeyer flask experiment and analyzing the hydrocarbon removal rate using gas chromatography, we found that Acinetobacter sp. D3-2 could grow at 30 °C in 3% NaCl solution with a preferable ability to degrade 82% hydrocarbons, showing that bioremediation does occur and plays a profound role during the oil reparation process.