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1.
Molecular analysis of cyanobacterial mat communities indicated that cyanobacteria, ammonia-oxidizing Archaea (AOA), and ammonia-oxidizing bacteria (AOB) coexist in those systems, competing for ammonium; this situation would imply competitive exclusion. We attempted to model how ammonia utilization niche partitioning occurs, and how ammonium levels can influence the interaction between those groups in a one-dimensional diffusionlimited system using Michaelis-Menten kinetics to describe ammonium consumption by each of those three groups. In our model, AOAs were able to dominate ammonium uptake by the community under most circumstances, except for unrealistically high (millimolar) levels of ammonium, where AOBs gained advantage. Cyanobacteria were unable to effectively compete for ammonium with either AOBs or AOAs throughout the mat at all ammonium concentrations and cell counts, suggesting that the presence of AOAs or AOBs forces cyanobacteria into nitrogen fixation mode. Such interaction can make cyanobacterial mats a net nitrogen source, as well as provide a carbon-independent energy transfer pathway from primary producers to the rest of the ecosystem.  相似文献   

2.
Estuarine nitrifiers: New players,patterns and processes   总被引：1，自引：0，他引：1  
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3.
A giant 800-m-diameter pockmark named REGAB was discovered on the Gabon continental margin actively emitting methane at a water depth of 3200 m. The microbial diversity in sediments from four different assemblages of chemosynthetic organisms, Mytilidae, Vesicomyidae, Siboglinidae and a bacterial mat, was investigated using comparative 16S rRNA gene sequence analysis. Aggregates of anaerobic methanotrophic archaea (ANME-2) and bacteria of the Desulfosarcina/Desulfococcus cluster were found in all four chemosynthetic habitats. Fluorescence in situ hybridization targeting the ANME-2/Desulfosarcina/Desulfococcus aggregates showed their presence few centimeters (3–5 cm) below the surface of sediment. 16S rRNA gene sequences from all known marine ANME groups were detected in the pockmark sediments, as well as from both known bacterial partners. The archaeal diversity was limited to the ANME cluster for all investigated samples. The bacterial diversity included members of the Proteobacteria, Bacilliales, Cytophaga/Flavobacteria, Verrucomicrobia, JS1 and Actinobacteria clusters. Bacterial 16S rRNA gene sequences related to those of known sulphide-oxidizing symbionts were recovered from tissues of several invertebrates including vesicomyid clams and siboglinid tubeworms of REGAB.  相似文献   

4.
The aim of this study is to investigate microbial structures and diversities in five active hydrothermal fields’ sediments along the Eastern Lau Spreading Centre (ELSC) in the Lau Basin (southwest Pacific). Microbial communities were surveyed by denatured gradient gel electrophoresis (DGGE) and clone library analysis of 16S rRNA genes. The differences in microbial community structures among sediment samples from the five deep-sea hydrothermal sites were revealed by DGGE profiles. Cluster analysis of DGGE profiles separated the five hydrothermal samples into two groups. Four different 16S rRNA gene clone libraries, representing two selected hydrothermal samples (19-4TVG8 and 19-4TVG11), were constructed. Twenty-three and 32 phylotypes were identified from 166 and 160 bacterial clones respectively, including Proteobacteria, Bacteroidetes, Firmicutes, Nitrospirae and Planctomycetes. The phylum Proteobacteria is dominant in both bacterial libraries with a predominance of Gamma-Proteobacteria. A total of 31 and 25 phylotypes were obtained from 160 and 130 archaeal clones respectively, including Miscellaneous Crenarchaeotic Group, Marine Group Ⅰ and Ⅲ, Marine Benthic Group E, Terrestrial Hot Spring Crenarchaeota and Deep-sea Hydrothermal Vent Euryarchaeota. These results show a variety of clones related to those involved in sulfur cycling, suggesting that the cycling and utilization of sulfur compounds may extensively occur in the Lau Basin deep-sea hydrothermal ecosystem.  相似文献   

5.
Using methods of molecular biology (PCR and cloning), we studied the diversity of microorganisms in the surface layers of bottom sediments from the bays of Gydan and Yenisei of the Kara Sea, which have different component composition of the pore water and mineralization level. Representatives of the domains Bacteria and Archaea were identified based on the analysis of the 16S rRNA gene fragment nucleotide sequences. The composition of the community of microorganisms in the bottom sediments changed with the changing salinity gradient of the pore waters. The phylogenetic analysis of the nucleotide sequences showed that the composition of the microbial communities in the southern parts of these bays was affected by fresh-water flows from rivers and streams from the lakes within the catchment area, whereas that in the northern parts was influenced by sea waters. The results indicate the presence of bacteria in the bottom sediments that are capable of using a wide range of substrates as a carbon source including hydrocarbons and organochlorine and aromatic compounds. These data can also indicate the presence of different pollutants in the sediments of these areas and the potential ability of bacteria to degrade chemical compounds that enter the waters and bottom sediments of the Kara Sea.  相似文献   

6.
对采自天津潮间带的污泥进行热休克处理,厌氧条件下富集混合菌群进行产氢试验;设置起始pH从4．0到8．0（间隔0．5个单位）,比较混合菌群在不同pH培养条件下产氢量;利用变性梯度凝胶电泳（DGGE）分析不同起始pH培养条件下的混合菌群组成。结果表明,在起始pH为7．0时,混合菌群产氢量最高。不同起始pH对产氢量的影响,依...  相似文献   

7.
The effect of kelp Ecklonia maxima inclusion in formulated feeds on abalone growth and gut bacterial communities has not been previously investigated in South Africa. An eight-month on-farm growth trial was conducted with sub-adult Haliotis midae (～43 mm shell length) fed graded levels of kelp in formulated feeds. Kelp inclusion (0.44–3.54% of pellet dry mass) promoted faster growth (65.7–74.5% total mass gain), with better feed and protein conversions (apparent feed conversion ratio [FCR] 1.4–1.8, apparent protein efficiency ratio [PER] 2.3–2.7), as compared with the non-supplemented feed (52.3% total mass gain, FCR 2.1, PER 1.9; p < 0.001). Abalone-gut bacterial DNA was sequenced using 16S rRNA gene pyrosequencing and the sequences were clustered into operational taxonomic units (OTUs) at a 97% similarity level. A supplementary 16S rRNA gene denaturing gradient gel electrophoresis (DGGE) analysis was employed. The dominant OTUs differed in terms of their relative abundances, with an autochthonous Mycoplasma strain being significantly more abundant (p = 0.03) in the gut of abalone fed a kelp-supplemented feed. The DGGE band patterns displayed higher within-group variability for abalone fed the control diet, suggesting that dietary kelp inclusion promotes gut-bacteria homeostasis. This may contribute to better feed utilisation and growth in abalone fed kelp-supplemented feeds.  相似文献   

8.
This paper synthesizes recent findings regarding microbial distributions and processes in the bathypelagic ocean (depth >1000 m). Abundance, production and respiration of prokaryotes reflect supplies of particulate and dissolved organic matter to the bathypelagic zone. Better resolution of carbon fluxes mediated by deep microbes requires further testing on the validity of conversion factors. Archaea, especially marine Crenarchaeota Group I, are abundant in deep waters where they can fix dissolved inorganic carbon. Viruses appear to be important in the microbial loop in deep waters, displaying remarkably high virus to prokaryote abundance ratios in some oceanic regions. Sequencing of 18S rRNA genes revealed a tremendous diversity of small-sized protists in bathypelagic waters. Abundances of heterotrophic nanoflagellates (HNF) and ciliates decrease with depth more steeply than prokaryotes; nonetheless, data indicated that HNF consumed half of prokaryote production in the bathypelagic zone. Aggregates are important habitats for deep-water microbes, which produce more extracellular enzymes (on a per-cell basis) than surface communities. The theory of marine gel formation provides a framework to unravel complex interactions between microbes and organic polymers. Recent data on the effects of hydrostatic pressure on microbial activities indicate that bathypelagic microbial activity is generally higher under in situ pressure conditions than at atmospheric pressures. High-throughput sequencing of 16S rRNA genes revealed a remarkable diversity of Bacteria in the bathypelagic ocean. Metagenomics and comparative genomics of piezophiles reveal not only the high diversity of deep sea microbes but also specific functional attributes of these piezophilic microbes, interpreted as an adaptation to the deep water environment. Taken together, the data compiled on bathypelagic microbes indicate that, despite high-pressure and low-temperature conditions, microbes in the bathypelagic ocean dynamically interact with complex mixtures of organic matter, responding to changes in the ocean’s biogeochemical state.  相似文献   

9.
Because the marine picoplanktonic communities are made up of phylogenetically different microbial groups, the re-evaluation of key processes such as bacterial secondary production (BSP) has become an important contemporary issue. The difficulty of differentiating the metabolic processes of Bacteria from the rest of the microorganisms in the water column (i.e., Archaea and Eukarya) has made it difficult to estimate in situ BSP. This work presents the seasonal variability of the prokaryote secondary production (PSP) measured by the incorporation of 14C-leucine in the oxygen minimum zone (OMZ) off central-southern Chile. The BSP and potential archaeal secondary production (PASP) were determined through the combined use of 14C-leucine and N1-guanyl-1, 7-diaminoheptane (GC7), an efficient inhibitor of archaeal and eukaryote cell growth. BSP accounted for the majority of the PSP (total average, 59 ± 7.5%); maximum values were ∼600 μg C m−3 h−1 and, on several dates, BSP represented 100% of the PSP. Similarly, PASP was also an important fraction of the PSP (total average, 42.4 ± 8.5%), although with levels that ranged from not detectable (on given dates) to levels that represented up to ∼97% of PSP (winter 2003). Our results showed that both Bacteria and Archaea accounted for almost equal portions of the prokaryote heterotrophic metabolism in the OMZ, and that PASP is notoriously enhanced through temporal pulses of heterotrophy. This indicates that, at least in marine systems with high abundance of Archaea (e.g., mesopelagic realm), the secondary production obtained through methods measuring the uptake of radiolabeled substrates should be considered as PSP and not as BSP. If the latter is the target measurement, then the use of an inhibitor of both archaeal and eukaryote cell growth such as GC7 is recommended.  相似文献   

10.
Anammox is the anaerobic oxidation of ammonium by nitrite or nitrate to yield N2. This process, along with conventional denitrification, contributes to nitrogen loss in oxygen-deficient systems. Anammox is performed by a special group of bacteria belonging to the Planctomycetes phylum. However, information about the distribution, activity, and controlling factors of these anammox bacteria is still limited. Herein, we examine the phylogenetic diversity, vertical distribution, and activity of anammox bacteria in the coastal upwelling region and oxygen minimum zone off northern Chile. The phylogeny of anammox bacteria was studied using primers designed to specifically target 16S rRNA genes from Planctomycetes in samples taken during a cruise in 2004. Anammox bacteria-like sequences affiliated with Candidatus “Scalindua spp.” dominated the 16S rRNA gene clone library. However, 62% of the sequences subgrouped separately within this cluster and together with a single sequence retrieved from the suboxic zone of the freshwater Lake Tanganyika. The vertical distribution and activity of anammox bacteria were explored through CARD-FISH (fluorescence in situ hybridization with catalyzed reporter deposition) and 15N labeling incubations, respectively, at two different open-ocean stations during a second cruise in 2005. Anammox bacterial CARD-FISH counts (up to 3000 cells ml−1) and activity (up to 5.75 nmol N2 L−1 d−1) were only detected at the station subjected directly to the upwelling influence. Anammox cell abundance and activity were highest at 50 m depth, which is the upper part of the OMZ. In this layer, a high abundance of cyanobacteria and a marked nitrogen deficit were also observed. Thus, our results show the presence of a new subcluster within the marine anammox phylogeny and indicate high vertical variability in the abundance and activity of anammox bacteria that could be related to an intensification of carbon and nitrogen cycling in the upper part of the OMZ.  相似文献   

11.
A sediment sample was collected from a deep-sea hydrothermal vent field located at a depth of 2 951 m on the Southwest Indian Ridge. Phylogenetic analyses were performed on the prokaryotic community using polymerase chain reaction（PCR） amplification of the 16 S rRNA and nifH genes. Within the Archaea, the dominant clones were from marine benthic group E（MBGE） and marine group I（MGI） belonging to the phyla Euryarchaeota and Thaumarchaeota, respectively. More than half of the bacterial clones belonged to the Proteobacteria, and most fell within the Gammaproteobacteria. No epsilonproteobacterial sequence was observed. Additional phyla were detected including the Actinobacteria, Bacteroidetes, Planctomycetes, Acidobacteria, Nitrospirae, Chloroflexi, Chlorobi, Chlamydiae, Verrucomicrobia, and candidate divisions OD1, OP11, WS3 and TM6, confirming their existence in hydrothermal vent environments. The detection of nifH gene suggests that biological nitrogen fixation may occur in the hydrothermal vent field of the Southwest Indian Ridge. Phylogenetic analysis indicated that only Clusters I and III NifH were present. This is consistent with the phylogenetic analysis of the microbial 16 S rRNA genes, indicating that Bacteria play the main role in nitrogen fixation in this hydrothermal vent environment.  相似文献   

12.
In marine wetlands, nitrogen fixation is a potentially important nutrient source for nitrogen‐limited primary producers, but interactions between nitrogen fixers and different vascular plant species are not fully understood. Nitrogen fixation activity was compared in sediments vegetated by three plant species, Spartina foliosa, Salicornia virginica, and Salicornia bigelovii in the Kendall Frost Reserve salt marsh in Mission Bay (CA). This study addressed the effects of plant type, day and night conditions, and sediment depths on nitrogen fixation. Higher rates of nitrogen fixation were associated with S. foliosa than with either of the two Salicornia spp., which are known to compete more effectively than Spartina for exogenous nitrogen in the salt marsh environment. Rates of nitrogen fixation, determined by acetylene reduction, in sediments vegetated by S. virginica were low during the day (7.7 ± 1.2 μmol C2H4 m−2 h−1) but averaged 13 ± 6.6 μmol C2H4 m−2 h−1 at night, with particularly high rates in samples from locations with visible cyanobacterial mats. The opposite diel pattern was found for sediments containing S. foliosa plants, in which average daytime and nighttime rates of nitrogen fixation were 62 ± 23 and 21 ± 15 μmol C2H4 m−2 h−1, respectively. For S. foliosa, nitrogenase activity of rinsed roots and different sediment sections (0–1, or 4–5 cm depths) were measured. Although nitrogen fixation rates in vegetated sediment samples were substantial, all but one of rinsed S. foliosa root samples (n = 12) and subsurface sediments at 4–5 cm depths failed to show nitrogen fixation activity after 2 h, suggesting that the most active nitrogen fixers in these systems likely reside in surface sediments. Further, nitrogenase activity in shaded and unshaded S. foliosa samples did not differ, suggesting that nitrogen fixers may not rapidly respond to changes in plant photosynthetic activity. Average nitrogen fixation rates in S. foliosa‐vegetated samples from the Mission Bay salt marsh were on the same order as those of highly productive Atlantic coast marshes, and this microbially‐mediated nitrogen source may be similarly substantial in other Mediterranean wetlands. Sediment abiotic variables seem to exert greater control upon nitrogen fixation activity than the effects of particular plant species. Nonetheless, dominant plant species may differ substantially in their reliance on nitrogen fixation as a nutrient source, with potentially important consequences for wetland conservation and restoration.  相似文献   

13.
赵珍  王宝杰  刘梅  蒋克勇  王雷 《海洋科学》2021,45(11):54-61
采用在模拟池塘中投放过硫酸氢钾复合物（KMPS）进行对比实验的方法,探究KMPS对养殖底质硝化作用的影响。通过对氨氮和亚硝态氮含量的检测,探究对不同时期氮素转化的影响,低频率高剂量投放组中的氨氮和亚硝态氮含量显著降低,而高频率低剂量组中氨氮和亚硝态氮的含量显著上升。高频率低剂量KMPS的投放使氨氧化古菌（AOA）和氨氧化细菌（AOB）丰度降低,而低频率高剂量KMPS的投放不会造成丰度降低,而且还表现出部分时期AOB丰度的上升。进一步对群落结构进行分析发现KMPS的投放使AOA群落中Nitrosopumilu属相对丰度降低,Nitrososphaera属的相对丰度上升,这种相对丰度的变化与KMPS的投放方式无关;但AOB群落受到KMPS投放方式的影响,低频率高剂量的KMPS投放下AOB群落优势属相对丰度显著提高。以上结果均说明低频率高剂量KMPS的投放起到了促进底质硝化作用的效果。同时,可为KMPS用于对虾养殖池塘底质改良开辟一个新的途径。  相似文献   

14.
Fresh and preserved (type material) specimens of the black ghost chimaera Hydrolagus melanophasma were compared for morphometric characteristics. A molecular comparison was also performed on two mitochondrial gene sequences (12S rRNA and 16S rRNA gene sequences). While significant differences in measurements were found, the differences were not attributable to sexual dimorphism or the quality of the specimens, but to the sample size and the type of statistical tests. The result of the genetic characterization showed that 12S rRNA and 16S rRNA genes represented robust molecular markers that characterized the species.  相似文献   

15.
北极深海沉积物中细菌和古菌群落结构研究   总被引：3，自引：0，他引：3  
在北极深海沉积物生态系统中,微生物的群落结构由有机质输入、能量的可用性及其他环境因素决定.然而,全球气候变暖及其导致的冰盖提前融化正在影响微生物的多样性.为描述北极深海沉积物中的微生物群落结构及其与环境因素的相关性,我们利用罗氏454对北极深海沉积物样品的16S rDNA扩增子进行了测序,对细菌和古菌群落的丰富度、成分、结构及其系统发育分类地位进行了描述.硫还原和化能有机营养类是细菌群落中的主要类群;而古细菌群落主要是由微生物的关系最为密切的氨氧化奇古菌门(96.66%)和产甲烷古生菌界(3.21%).这项研究描述了北极极点附近深海沉积物(> 3500米)中的微生物多样性,将为以后研究类似环境中微生物代谢过程和途径等功能分析奠定基础.  相似文献   

16.
Macroalgal mats commonly occur in estuaries and sheltered embayments where they are thought to affect the oxygen conditions in the sediment, influence the geochemical process and influence the burrowing activity of bivalves. Laboratory experiments evaluated the effects of sediment hypoxia and algal mats on the burrowing ability and survival of the New Zealand cockle Austrovenus stutchburyi at 15 °C. Both dissolved oxygen concentration and time affected the burial depth of the cockles over the 12 days of the experiment. In hypoxic conditions (<2 mg L?1), cockles migrated to the sediment surface after 3.5 days and mortality occurred after 11 days. Bivalves exposed to oxygen concentrations of 2–3 mg L?1 buried closer to the sediment surface than those in the other treatments. Using a simulated tidal regime, in a mesocosm, burrowing behaviour of the cockle and pore-water oxygen conditions in the sediment were measured on exposure to experimental mats of Gracilaria chilensis and Ulva spp. for over 6 days. Algal mats on the surface of the sediment significantly lowered the dissolved oxygen concentration of the sediment pore-water and this effect was greater for the Ulva spp. treatment than the G. chilensis treatment. Cockles were buried more deeply in the control treatment without algae than in either of the two algal treatments. It is concluded that reduced oxygen conditions (<3.5 mg L?1) develop under macroalgal mats and that this reduces the burial depth of cockles. The potential harmful effects of the mats can depend on the species forming the mat and these effects are likely to be greater in the field than they are in controlled laboratory conditions.  相似文献   

17.
Microbial mats were collected from a variety of sites near hydrocarbon vents along the slope in the northern Gulf of Mexico and, for comparison, from Warm Mineral Springs, Florida, USA. A predominant microorganism in each of the mats was the giant bacterium,Beggiatoa. Diameters of the bacterial filaments ranged from about 6 µm to approximately 200 µm. The latter organisms are the largest prokaryotic organisms yet found. All filaments over about 10 µm in diameter contained a large central vacuole, producing a cell with the cytoplasm as a cylindrical tube underlying the cytoplasmic membrane. Sulfur globules were confined to this peripheral layer. Push cores often contained pyrite tubules whose appearance is suggestive of aBeggiatoa origin. Determinations of 13C inBeggiatoa mats from vents along the Louisiana slope yielded values in the range of –26.6 to –27.9 (PDB), suggesting an unusually high degree of isotope fractionation (–24.9) relative to the carbon source in the ambient seawater, which is typical of sulfur-oxidizing chemoautotrophs. The presence of SO (elemental sulfur) within cells ofBeggiatoa resulting from oxidation of H2S supports the importance of bacterial sulfate reduction processes in the underlying vents for the sustenance of theBeggiatoa mats.  相似文献   

18.
The taxonomy of oysters has been traditionally based on characteristics of the shell. More recently, the analysis of protein and DNA polymorphism has provided a means to overcome difficulties in distinguishing the different species of oysters based solely on shell morphology. In order to identify oysters of the Tunisian north-east coast, we sequenced a 16S rRNA mitochondrial fragment from 68 oysters sampled from the Bizert Lagoon and the Gulf of Hammamet in northern Tunisia. Comparison of oyster 16S rRNA sequences available in GenBank showed the presence of both Ostreola stentina and Crassostrea gigas in our samples, which could not be detected on the basis of shell morphology only. These data confirmed that C. gigas, a non-native species, is now naturalised in the Bizert Lagoon. Furthermore, significant levels of genetic divergence among the 16S rRNA haplotypes from O. stentina populations have been observed. Specifically, the haplotypes found in the Bizert Lagoon are closer to those previously detected from Morocco and Portugal, whereas those in the Gulf of Hammamet are closer to the haplotypes from the south of Tunisia, with a divergence ranging from 2.1% to 2.7% between the northern and eastern Tunisian haplotypes. The possible impact of the Siculo-Tunisian Strait on the phylogeography of O. stentina is discussed.  相似文献   

19.
传统的形态鉴定主要依赖于分类者的经验和水平,容易产生分类错误。为提高物种鉴定的准确性,作者采用形态学与线粒体16S rRNA基因序列分析相结合的方式对广西北海涠洲岛采获的3种珍珠贝进行了鉴定。研究结果表明,基于形态学可将3种珍珠贝分别鉴定为企鹅珍珠贝(Pteria penguin)、宽珍珠贝(P.loveni)和中国珍珠贝(P.chinensis),但基于16S r RNA基因序列,形态学鉴定为P.loveni的标本应为P.lata。P.loveni和P.lata是两个完全独立的种,并非为同物异名。珍珠贝属16S rRNA基因序列的种间遗传距离明显大于种内遗传距离,适宜作为该属种类鉴定的分子标记。在基于16S r RNA基因序列构建的系统树中,相同种类的不同个体均形成单系群,并获得很高的支持率。分布于中国沿海的珍珠贝属种类应包括P.lata,是否有P.loveni的分布尚需进一步证实。  相似文献   

20.
To understand the temporal and spatial variation of the prokaryotic community in the East Sea, their composition was determined by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE)-sequencing techniques. The investigations were conducted twice annually in 2007 and 2009 in coastal and offshore stations. Prokaryotic abundance (PA), leucine incorporation rate, and other environmental parameters were also measured. By using the DGGE approach, we obtained 283 bacterial sequences and 160 archaeal sequences. The most frequently detected bacterial phylotypes during the investigations belonged to Alphaproteobacteria, Gammaproteobacteria, and Bacteroidetes. However, their relative compositions differed in time and space. Although Alphaproteobacteria and Bacteroidetes were the dominant groups in the surface water in May 2007 and in May and October 2007, Gammaproteobacteria was dominant in mesopelagic samples. However, Gammaproteobacteria was overwhelmingly dominant in most samples in August 2009. Although Deltaproteobacteria was rarely found as a dominant bacterial group, it occupied the highest fraction in a mesopelagic sample in October 2007. Epsilonproteobacteria also showed a similar trend, although its maximal dominance was found in a mesopelagic sample in August 2009. The archaeal community was dominated overwhelmingly by members of the Euryarchaeota in most of the investigations. However, Nitrosopumilales was dominant in aphotic samples in August 2009. Further, their spatiotemporal composition at the family level changed more dynamically in the East Sea. These temporal and spatial distributions of the prokaryotic community were influenced mainly by seawater temperature and depth in the East Sea.  相似文献   

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