Mangrove Sediment Samples Research Articles

Characterization of alkaline protease enzyme produced from marine yeast Candida orthopsilosis AKB-1 and its applications.

The present study has undertaken the isolation of marine yeasts from mangrove sediment samples and their ability to produce alkaline protease enzymes. A total of 14 yeast isolates were recovered on yeast-malt agar (YMA) and yeast extract peptone dextrose (YEPD) agar medium. After screening for proteolytic activity on skim milk agar, marine yeast isolate, AKB-1 exhibited a hydrolysis zone of 18mm. Optimal conditions for the enzyme production from yeast isolate AKB-1 were at 30°C, pH 8, fructose as carbon source, potassium nitrate as nitrogen source, and 25% saline concentration. Under the optimal conditions, the protease enzyme activity of the isolate AKB-1 was observed to be 978IU/mL. The structural and functional analysis was carried out through FTIR and HPLC analysis for the extracted protease enzyme. Furthermore, the enzyme produced was partially purified by solvent extraction using ethyl acetate and ammonium sulfate precipitation (3.4-fold) followed by dialysis (56.8-fold). The molecular weight of the purified enzyme was observed to be around 60kDa using SDS-PAGE. The extracted protein showed good antibacterial activity against six different clinical bacterial pathogens and the highest against Bacillus cereus (16 ± 0.5mm). The extracted protease enzyme was revealed to remove blood stains from cloth within 20min of application similar to the commercial detergent. The marine yeast isolate was further identified as Candida orthopsilosis AKB-1 (Accession number KY348766) through 18S rRNA sequencing, and a phylogenetic tree was generated.

Genome sequence of Sulfurimonas sp. C5, a potential chemolithoautotrophic, sulfur-oxidizing bacterium isolated from a mangrove sediment.

Sulfurimonas sp. strain C5 (MCCC 1A19556) is a strain with potential chemolithoautotrophic sulfur-oxidizing function, which is isolated from a mangrove sediment sample collected from Quanzhou Bay, Fujian Province, China. This report describes the genome sequence of strain C5, which possesses the gene sets for the sulfur-oxidizing pathway.

Metagenomic 16S rRNA analysis and predictive functional profiling revealed intrinsic organohalides respiration and bioremediation potential in mangrove sediment

BackgroundMangrove sediment microbes are increasingly attracting scientific attention due to their demonstrated capacity for diverse bioremediation activities, encompassing a wide range of environmental contaminants.Materials and methodsThe microbial communities of five Avicennia marina mangrove sediment samples collected from Al Rayyis White Head, Red Sea (KSA), were characterized using Illumina amplicon sequencing of the 16S rRNA genes.ResultsOur study investigated the microbial composition and potential for organohalide bioremediation in five mangrove sediments from the Red Sea. While Proteobacteria dominated four microbiomes, Bacteroidetes dominated the fifth. Given the environmental concerns surrounding organohalides, their bioremediation is crucial. Encouragingly, we identified phylogenetically diverse organohalide-respiring bacteria (OHRB) across all samples, including Dehalogenimonas, Dehalococcoides, Anaeromyxobacter, Desulfuromonas, Geobacter, Desulfomonile, Desulfovibrio, Shewanella and Desulfitobacterium. These bacteria are known for their ability to dechlorinate organohalides through reductive dehalogenation. PICRUSt analysis further supported this potential, predicting the presence of functional biomarkers for organohalide respiration (OHR), including reductive dehalogenases targeting tetrachloroethene (PCE) and 3-chloro-4-hydroxyphenylacetate in most sediments. Enrichment cultures studies confirmed this prediction, demonstrating PCE dechlorination by the resident microbial community. PICRUSt also revealed a dominance of anaerobic metabolic processes, suggesting the microbiome’s adaptation to the oxygen-limited environment of the sediments.ConclusionThis study provided insights into the bacterial community composition of five mangrove sediments from the Red Sea. Notably, diverse OHRB were detected across all samples, which possess the metabolic potential for organohalide bioremediation through reductive dehalogenation pathways. Furthermore, PICRUSt analysis predicted the presence of functional biomarkers for OHR in most sediments, suggesting potential intrinsic OHR activity by the enclosed microbial community.

Phylogenomic evaluation of Mangrovimicrobium sediminis gen. nov. sp. nov., the first nitrogen fixing member of the family Halieaceae adapted to mangrove habitat and reclassification of Halioglobus pacificus to Pseudohaliglobus pacificus comb. nov.

The taxonomic position and genomic characteristics of a nitrogen fixing and polymer degrading marine bacterium, strain SAOS 164 isolated from a mangrove sediment sample was investigated. Sequence analysis based on 16S rRNA gene identified it as a member of family Halieaceae with closest similarity to Haliea salexigens DSM 19537T (96.3 %), H. alexandrii LZ-16-2T (96.2 %) and Parahaliea maris HSLHS9T (96.0 %) but was distantly related to the genera Haliea, Parahaliea and Halioglobus in phylogenetic trees. In order to ascertain the exact taxonomic position, phylogeny based on RpoBC proteins, whole genome, core and orthologous genes, and comparative analysis of metabolic potential retrieved the strain in an independent lineage clustering along with the genera Halioglobus, Pseudohalioglobus and Seongchinamella. Further, various genome based delimitation parameters represented by mol % GC content, percentage of conserved proteins (POCP), and amino acid identity (AAI) along with chemotaxonomic markers (i.e. fatty acids and polar lipids) supported the inferences of genome based phylogeny and indicated that the strain SAOS 164 belongs to a novel genus. The genome was mapped to 4.8 Mb in size with 65.1 % DNA mol% G + C content. In-silico genomic investigation and phenotyping revealed diverse metabolite genes/pathways related to polymer hydrolysis, nitrogen fixation, light induced growth, carbohydrate, sulfur, phosphorus and amino acid metabolism, virulence factors, defense mechanism, and stress-responsive elements facilitating survival in the mangrove habitat. Based on polyphasic taxonomic approach including genome analyses, a novel genus Mangrovimicrobium sediminis gen. nov. sp. nov. (=SAOS 164T = MTCC 12907T = KCTC 52755T = JCM 32136T) is proposed. Additionally, the reclassification of Halioglobus pacificus (=DSM 27932T = KCTC 23430T = S1–72T) to Pseudhalioglobus pacificus comb. nov. is also proposed.

Human activities altered the enrichment patterns of microplastics in mangrove blue carbon ecosystem in the semi-enclosed Zhanjiang Bay, China

Mangroves, as the key blue carbon ecosystem, are considered ‘potential sinks’ for microplastics (MPs) in the land-ocean interface zones. However, there is limited understanding of enrichment patterns of MPs in mangrove blue carbon ecosystem, particularly in relation to human activities. This study explored the abundance, composition, and diversity of MPs in mangrove and non-mangrove sediments in Zhanjiang Bay (ZJB) to investigate the effects of human activities on MPs enrichment patterns in the blue carbon system. The results showed that MPs were widely prevalent in all sediment samples, and the abundance of MPs was significantly higher in all mangrove sediments than in non-mangrove sediments (P < 0.05). Furthermore, the average abundance of MPs was found to be 263.67 ± 85.25 items/kg in non-mangrove sediment samples, whereas in mangrove sediment samples, it was 618.17 ± 71.75 items/kg. The average abundance of MPs in mangroves was about 1.6 times higher than that in non-mangroves, indicating that mangroves have an interception effect on MPs, and human activities are the key factor leading to the difference in MPs enrichment patterns between mangroves and non-mangroves. Furthermore, the predominant MPs shapes in both mangroves and non-mangroves are fragments, with multicolor and green being the most common colors and most MPs sizes ranging between 100 and 330 µm. Besides, there was no significant relationship found between MPs abundance and particulate organic carbon (P > 0.05), indicating that MPs pollution didn’t significantly alter the natural POC pool in ZJB. Overall, this study provided important baseline information on MPs pollution in the mangrove blue carbon ecosystems in ZJB, which was implications for future mitigation of MPs pollution and the management of mangrove ecosystem.

Characterization of polycyclic aromatic hydrocarbons in mangrove sediments from Ifiekporo Creek, Warri, Nigeria

The occurrence and level of polycyclic aromatic hydrocarbons (PAHs) in mangrove sediment from Ifiekporo Creek in Warri, Delta State, Nigeria, were assessed in this study. The extraction of PAHs from the sediment samples was achieved using the PAH analytical test method (USEPA 8270). This method measures the individual concentrations of extractable PAHs in samples. The PAHs were quantified within the C11-C22 subgroup. The basic GC parameters for the analysis of polyaromatic hydrocarbons were analysed using a gas chromatography‒mass selective detector (GC‒MSD). The individual PAH concentrations in the mangrove sediment samples ranged from 850 µg/kg−1 to 3470 µg/kg−1. PAH source apportionment employing isomeric ratios and multivariate statistics indicated both pyrogenic and petrogenic source inputs in the sediment samples. The order of PAH homology in the sediment was 3-ring > 2-ring > 4-ring. The sediment samples were mostly dominated by LMW PAHs. The results of the ecological risk assessment in the study area indicate that there is low ecological risk associated with PAH exposure in sediment. These results provide data on the concentrations and compositional patterns of PAHs, which is useful for understanding the effects, sources, fates, and transport of PAHs in sediment in the study area, as well as for providing relevant information for environmental quality management and forensic studies.

Assessment of heavy metal distribution, risk, and sourcing in mangrove sediments from three Saudi Arabian Red Sea locations

This work measured the concentration of heavy metal cations (V, Cr, Ni, Cu, Zn, Cd, and Pb) and associated anionic ligands (SOM, carbonate, and silicate) in mangrove sediment samples from the Red Sea of Saudi Arabia to set a biogeochemical baseline within these as yet poorly constrained sensitive ecosystems. Sediments were collected from three regions along the Saudi Arabian coast: Yanbu, Jeddah, and the Farasan Islands. Risk indices and statistical analyses were applied to assess contamination levels and potential sourcing. Results show that Yanbu is at environmental risk as it shows higher concentrations and anthropogenic signatures for most metals (Cr, Cu, Zn, Cd and Pb) compared to the other two regions. Jeddah metal concentrations are similar to the Islands; however, the statistical analyses suggest that a singular anthropogenic source controls heavy metal delivery to its environment.

Characterization of two novel Fe(III)-reducing and electrogenic bacteria, Shewanella ferrihydritica sp. nov. and Shewanella electrica sp. nov., isolated from mangrove sediment.

Three novel strains in the genus Shewanella, designated A3AT, C31T and C32, were isolated from mangrove sediment samples. They were facultative anaerobic, Gram-stain-negative, rod-shaped, flagellum-harbouring, oxidase- and catalase-positive, electrogenic and capable of using Fe(III) as an electron acceptor during anaerobic growth. Results of phylogenetic analysis based on 16S rRNA gene and genomic sequences revealed that the strains should be assigned to the genus Shewanella. The 16S rRNA gene similarity, average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the isolates and their closely related species were below the respective cut-off values for species differentiation. The 16S rRNA gene similarity, ANI and dDDH values between strains C31T and C32 were 99.7, 99.9 and 99.9 %, respectively, indicating that they should belong to the same genospecies. Based on polyphasic taxonomic approach, two novel species are proposed, Shewanella ferrihydritica sp. nov. with type strain A3AT (GDMCC 1.2732T=JCM 34899T) and Shewanella electrica sp. nov. with type strain C31T (GDMCC 1.2736T=JCM 34902T).

Defluviimonas sediminis sp. nov., isolated from mangrove sediment.

A Gram-stain-negative, facultatively aerobic, motile and ovoid- to rod-shaped bacterium, designated as FT324T, was isolated from a surface mangrove sediment sample from Shenzhen, PR China. The taxonomic position of strain FT324T was determined by a combination of phylogenetic, physiological, biochemical and chemotaxonomic analyses. Strain FT324T grew at 20-40 °C (optimum, 30-37 °C), pH 5.0-9.0 (optimum, pH 8.0) and in the presence of 0-3 % (w/v) NaCl (optimum, 1 %). Its full-length 16S rRNA gene sequence was the most similar to Frigidibacter oleivorans XJ4T (97.4 %), followed by Defluviimonas denitrificans DSM 18921T (96.62 %), Pseudothioclava arenosa CAU 1312T (96.54 %) and Defluviimonas nitratireducens DL5-4T (96.47 %). The major fatty acids (>10 %) of FT324T were C19 : 0 cyclo ω8c (51.9 %) and summed feature 8(29.6 %). The predominant respiratory quinone was Q-10. Its polar lipid profile contained phosphatidylethanolamine, phosphatidylmethylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified aminolipid, one unidentified lipid and two unidentified phospholipids. Its estimated genome size was 4 294 115 bp and the genomic DNA G+C content was 69.6 mol%. Based on its distinct phenotypic, chemotaxonomic and phylogenetic characteristics, strain FT324T should represent a novel species of the genus Defluviimonas, for which the name Defluviimonas sediminis sp. nov. is proposed (=MCCC 1K07685T=KCTC 92477T).

Mangrove (Avicennia marina) parts as proxies in marine pollution of Nizampatnam Bay, East Coast of India: An integrated approach

This study focuses on the assessment of heavy metals (HM) concentration and pollution status of the Nizampatnam Bay, east coast of India, from mangrove plant parts (roots and leaves) and sediment samples. This is the first of its kind work (comparison of data from both mangrove and sediment samples) from the third largest mangrove ecosystem in India. To carry out this work, plant (Avicennia mariana) and sediment samples were collected from five stations. The collected samples were carefully subjected to the laboratory methods and heavy metal concentrations were determined by using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The obtained results were juxtaposed with the optimal values of world surface pollution rock averages, and noticed heavy metals such as Cd and Cu exceed the optimal values. To know the contamination levels and the chemical elements that contribute to the pollution, various environmental indices, viz., contamination factor, enrichment factor, geoaccumulation index, and pollution load index were, carried out on the sediment sample data. To ascertain the mangrove plant's capacity (in the study area) for accumulation and translocation of heavy metals in different parts of the plants, factors such as bio-concentration and translocation were calibrated.

Spectral features of Fe and organic carbon in estimating low and moderate concentration of heavy metals in mangrove sediments across different regions and habitat types

Soil or sediment spectral reflectance do not directly reflect information of spectrally featureless heavy metals. With mangrove sediment samples collected in five regions and four habitat types, this study aimed to explore the spectral features related to spectrally active constituents (Fe and organic carbon (OC)) in estimating low and moderate concentrations of four heavy metals (Cr, Ni, Cu and Pb). A total of 27 modeling strategies using XGBoost (extreme gradient boosting) model were compared for estimating each heavy metal: three types of spectral features (Fe, OC and heavy metal) * three spectral transformation methods (Log(1/R), first derivative (FD) and continuous wavelet transform (CWT)) * three variable selection methods (genetic algorithm (GA), successive projection algorithm (SPA) and recursive feature elimination (RFE)). The results showed that the combination of CWT and RFE was recommended for heavy metal estimation, and the ranking of model accuracy was Cu > Pb > Ni > Cr. The optimal XGBoost model was found using spectral features related to Fe for Cr (RVal2(determination coefficient of independent validation) = 0.42, RMSE (root mean square error) = 0.32 and RPIQ (the ratio of performance to interquartile range) = 1.53) and Cu estimation (RVal2 = 0.87, RMSE = 0.19 and RPIQ = 2.20), spectral features related to OC for Ni estimation (RVal2 = 0.63, RMSE = 0.26 and RPIQ = 2.38) and spectral features related to Pb itself for Pb estimation (RVal2 = 0.82, RMSE = 0.23 and RPIQ = 2.59). Moreover, the XGBoost model transferability across different habitat types outperformed that across different regions and data ranges of Fe and OC. We conclude that the modeling strategy using spectral features related to spectrally active constituents has great potentials in quantifying low and moderate concentration of sediment heavy metals, and the samples with high Fe concentration (31.62–37.29 g kg−1) are recommended to improve estimation accuracy of low and moderate concentrations of heavy metals, which could provide sampling strategy development and early warning of heavy metal pollution in mangrove ecosystem.

Shewanella shenzhenensis sp. nov., a novel Fe(III)-reducing bacterium with abundant possible cytochrome genes, isolated from mangrove sediment.

A facultative anaerobic bacterium, designated as A25T, was isolated from a mangrove sediment sample collected in Shenzhen, China. Cells of strain A25T were found to be Gram-staining negative, rod-shaped, flagella-harboring, and oxidase- and catalase-positive. The isolate was able to grow at 4-40°C (optimum 28°C) and pH 5.0-9.0 (optimum pH 6.0), and in 0-10% NaCl concentration (w/v) (optimum 1%). Strain A25T was capable of reducing Fe(III) citrate under anaerobic conditions. The major fatty acids of this strain was C16:1ω7c/C16:1ω6c (summed feature 3), C17:1ω8c and iso-C15:0. Results of phylogenetic analyses based on 16S rRNA gene sequences indicated that strain A25T is affiliated with the genus Shewanella, showing the highest similarity to Shewanella seohaensis S7-3T (98.4% similarity). The average nucleotide identity and digital DNA-DNA hybridization values between the genomes of strain A25T and its closely related strains were ≤ 79.0% and ≤ 22.8%, respectively. Based on its phenotypic, phylogenetic properties and physiological and biochemical characteristics, strain A25T (= JCM 34900T = GDMCC 1.2731T) was designated as the type strain of a novel species of the genus Shewanella, for which the name Shewanella shenzhenensis sp. nov. was proposed.

Tidal variation shaped microplastic enrichment patterns in mangrove blue carbon ecosystem of northern Beibu Gulf, China

Mangroves are considered to be a sink for microplastics (MPs) due to their unique characteristics. Previous studies mainly focused on the spatial distribution of MPs, but few researchers have addressed the influence of tidal variation on this distribution, especially since the MP total number in mangroves was unknown. In this study, surface sediment samples were collected in mangroves from the Beibu Gulf, South China Sea, and the abundance, composition, and number of MPs were investigated. The results showed that MPs were widely present in all mangrove sediment samples, with abundances ranging from 26.67 ± 9.43 to 239.94 ± 37.80 items/kg. The distribution of MPs was heterogeneous among different sampling sites, with the highest levels in the Shankou (SK) area. The MP abundance in the same mangrove forest gradually increased from the low tidal zone to the high tidal zone, with the enrichment factor ranging from 1.50 to 4.00. The MP abundance was significantly correlated with particulate organic carbon (POC) (n = 12, R = 0.664, p < 0.05). Results showed that mangroves had an interception effect on MPs and factors affecting MP distribution in mangrove sediments included not only tides but also human activities, such as aquaculture, agriculture, and residential life. Finally, this paper estimated the MP total number in mangroves at different sampling areas and tidal zones, and the middle tidal zone was considered to be more accurate for MP pollution assessment in mangroves.

Yeast Diversity in the Mangrove Sediments of North Kerala, India

Objective: Mangrove sediments, due to their unique environment, are considered to be a crucial habitat in identifying yeast strains with potent industrial, biotechnological and bioremediation properties. The goal of the current study was to understand the presence, diversity and hydrolytic enzyme properties of yeasts from the mangrove sediments of North Kerala. Materials and Methods: Sampling was done during the period 2018-2020 from mangrove sediments of 5 districts along the North Kerala coast. Isolation of yeast was done on yeast glucose peptone agar, and isolates were tested for their potential for the production of extracellular enzymes viz. amylase, cellulase, chitinase, DNase, lipase, ligninase, pectinase, protease and urease, using standard media with specific substrates. Morphological assessment, biochemical characterization and molecular identification of the isolates were performed. The phylogenetic tree of the selected yeast strains was constructed with the Maximum Likelihood method using MEGA X software. Results: A total of 482 yeast strains belonging to 12 genera were obtained from the mangrove sediment samples, the most dominant genera being Candida (56.3%). Kluveromyces, Debaromyces, Torulaspora, Trichosporon, pigmented yeast Rhodotorula, Cyberlindnera, Wickerhamiella, Pichia, Trichoderma, Meyerozyma and Kodamaea were the other genera identified. The majority of the yeast present in the mangrove sediment samples were lipolytic (68%), followed by ureolytic (23%), ligninolytic (16%), cellulolytic (9%), DNAlytic (9%), proteolytic (8%), amylolytic (6%), pectinolytic (4%) and chitinolytic (2%) forms. All 12 genera of yeast obtained had positive forms for extracellular lipase. Conclusion: The yeast strains obtained from mangrove sediments in the study were found to be ecologically important and have great biotechnological potential.

Reflectance spectroscopy for assessing heavy metal pollution indices in mangrove sediments using XGBoost method and physicochemical properties

Single and composite pollution indices (SPI and CPI) of heavy metals are calculated with background heavy metal concentrations. They are efficient evaluation indicators of sediment pollution levels and could be directly compared among different regions and habitat types, however, they are rarely investigated in mangrove sediment with visible and near-infrared spectroscopy (VNIRS). With mangrove sediment samples collected from five regions and four habitat types, this study aimed to develop estimation models of heavy metal (Cr, Ni, Cu, Zn and Pb) pollution indices using XGBoost (extreme gradient boosting) method, and further to explore the effect of physicochemical properties (Fe, organic carbon (OC), clay and salinity) on the estimation accuracy. Kruskal-Walls test showed that regions and habitat types were significant factors affecting the six pollution indices. Compared with first derivative, second derivative and continuum removal reflectance, standard normal variate (SNV) reflectance was more accurate for estimating SPIs and CPI using XGBoost model. The XGBoost models with sensitive wavelengths of SNV reflectance outperformed that with whole spectrum (410 bands) in estimating the six pollution indices, and the ranking of estimation accuracy was CPI > SPICu > SPIZn > SPIPb > SPINi > SPICr. Compared with the XGBoost model with sensitive wavelengths alone, the model with additional physicochemical properties could increase R2 and RPD (the ratio of standard deviation to RMSE of validation in the test subset) values by 0.795–7.282% and 1.199–8.780%, and decrease RMSE values by 4.101–26.866% in estimating SPICr, SPINi and SPICu. Moreover, Fe and OC had greater effect on the estimation accuracy than clay and salinity. We conclude the integration of XGBoost and physicochemical properties holds potentials for accurately assessing heavy metal pollution indices in mangrove sediment with VNIRS, which can provide methodological basis for evaluating environment quality and ecological risk in mangrove ecosystem at the plot or landscape scale.

Profiling bacteriome associated with the sediments of a mangrove ecosystem in Kerala, India

Microbiomes play an essential role in maintaining the health of an aquatic ecosystem. The present study is an attempt to analyze the bacteriome of a mangrove ecosystem in Cochin, Kerala, India. 16S rRNA gene-based high throughput sequencing revealed distinct and diverse bacterial communities present in the mangrove sediment sample. The taxonomic approaches applied revealed the dominance of Proteobacteria, Bacteroidetes and Firmicutes in the sample, followed by Actinobacteria, Cyanobacteria, Chloroflexi, Acidobacteria, Saccharibacteria (TM7) and Verrucomicrobia. At the genus level, Prevotella copri and Bacteroides fragilis dominated the sediment sample, which was followed by Pseudomonas, Bifidobacteria, Faecalibacterium, Agrobacterium, Acinetobacter, Streptococcus and Bacillus. Most of these organisms are predominantly found in the human intestine and human faeces and are found in polluted areas. Vibrio harveyi, a potential pathogen that results in mass mortality of mangrove associated organisms, could also be detected. Archaea only accounted for <1% of the metagenome and included Crenarchaeota, Euryarchaeota and unclassified ones. Unclassified bacteria also contributed a portion of the metagenome. The data obtained in the current study indicated that anthropogenic activities and micro-niche play an essential role in structuring the bacterial community. The results of the present study add valuable baseline data on the bacteriome of the mangrove sediments.

Susceptibility pattern of methicillin resistance Staphylococcus aureus (MRSA) by flow cytometry analysis and characterization of novel lead drug molecule from Streptomyces species

BackgroundActinomycetes particularly, Streptomyces species are producing wide variety of natural products with potential bioactivities. The microbial-derived metabolites hold a strong position to combat emerging and re-emerging antimicrobial drug-resistant pathogens. ObjectivesA diverse group of actinomycetes strains were isolated from unexplored regions of mangrove sediment. Further, a polyphasic approach based on 16S rRNA gene sequence analysis and to evaluate their antibacterial potential against a panel of bacterial pathogens and methicillin resistance Staphylococcus aureus (MRSA). MethodsThe mangrove sediment samples were serially diluted with sterile water and plated on inorganic starch agar medium. A total of 20 isolates were pure cultured and 16S rRNA gene sequences were deposited in the public nucleotide databases (GenBank, NCBI). All the isolates were screened for the antibacterial activity by agar overlay method. Further, the susceptibility pattern of MRSA by flow cytometry and fluorescence microscopy was analysed. ResultsThese twenty different isolates were grouped under nine major clad and they shared 95–99% sequence identity to the 16S rRNA gene sequences of the genus Streptomyces in the public nucleotide databases. Among these strains, the isolates namely JRG-02, JRG-03, JRG-04, JRG-10 and JRG-12 exhibited a broad-spectrum antibacterial activity against Methicillin-resistant Staphylococcus aureus(MRSA) and Gram negative bacteria Klebsiella pneumoniae MTCC109. Furthermore, we have characterized the antibacterial compound production and its properties from the isolate JRG-02, a potential drug candidate. The culture conditions and various nutrient components of strain Streptomyces sp. JRG-02 were optimized for enhanced antibiotics production of the isolate. The FT-IR and LCMS spectrum analysis envisaged the chemical nature of the substance. The effect of antibacterial compound on the viability of MRSA was alone examined by flow cytometry (FACS) and fluorescence microscopy analysis. ConclusionsThe present study clearly shows that the survival of diverse inhabitants of Streptomyces in the mangrove sediments. Hence, the mangrove sediment inhabiting strain Streptomyces sp. JRG-02 has potential pharmaceutical activity and genetic diversity.

Ecological interception effect of mangroves on microplastics

As the last barrier preventing river pollutants from entering the ocean, mangroves have strong absorption and purification abilities, and strong tolerance. We collected mangrove surface water and sediment samples from the Xixi Estuary of Xiamen city. The results showed that the abundance of microplastics in seawater ranged from 620 to 13,100 n/m3, the abundance of microplastics in sediment ranged from 143 to 488 n/kg, the distribution of microplastics was uneven, and the abundance of microplastics in the Xixi Estuary mangrove was significantly higher than that in the non-mangrove area. The sediment column sample results also showed that microplastics were detected in each layer of the sediments, indicating that microplastics were trapped in each layer of mangrove sediments. Therefore, we believe that mangrove forests have an ecological interception effect on microplastics. After entering mangroves, microplastics are affected by tidal reciprocating current scouring, river runoff, sunlight, wind erosion and other factors and gradually break into increasingly smaller particles through physical, chemical and biological effects. Microplastics accumulate in the sediments and experience sedimentation, suspension and reprecipitation processes together with the surface sediments. Mangroves should be widely planted in estuaries to reduce microplastic entry into the ocean.

Microplastics on beaches and mangrove sediments along the coast of South China

Accumulation of microplastics (MPs) data on a global scale is key to supporting plastic waste management for protecting ecosystems. To respond this call, a sampling campaign was conducted in the summer and winter seasons of 2018 to collect beach and mangrove sediment samples from 32 sites along the coastline of South China. The MPs concentrations in the intertidal zone along the coast of South China were comparable to those in other regions around the world. Polystyrene foams and fibers were the most abundant debris in the 0.2–5 mm and 0.02–2 mm MPs, respectively. Principal component and correlation analyses indicated that the abundances of MPs were related to wind direction, wastewater discharge amount, and tourist and fishing activities. Risk assessments suggested that potential ecological risks induced by MPs on beaches and mangrove forest along the coast of South China should not be overlooked.

Isolation, Characterization and Application of Protease Enzyme from Marine Bacteria

Protease constitutes the major group of catalytic enzymes which is involved in hydrolyzing peptide bond of proteins. Marine sediment sample were collected and protease producing bacterial isolates were identified by using casein as a substrate. The organisms were characterized by biochemical test and identified as Bacillus sp. In order to check for the production of protease enzyme, quantitative protease assay and Lowry’s method of protein estimation was carried out. The crude extract of protease was subjected for blood stain removal activity and the enzyme proved to be efficient which removed the stain in 15 min. The purpose of the current study is to isolate, identify, characterize and to carry out applications of protease enzyme from marine bacteria isolated from mangrove sediment samples.