Degradation and utilization of protein derived from <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> by marine microbial community

Microbial degradation and utilization of proteins derived from bacterial detritus were investigated in a microcosm experiment using Pseudomonas aeruginosa detritus as a substrate. To assess the effects of natural marine microbial communities on degradation and utilization of protein derived from P. aeruginosa cells, four microcosms were prepared: natural seawater (containing the natural microbial community) with P. aeruginosa detritus (N+Pa), autoclaved seawater with P. aeruginosa detritus (A+Pa), natural seawater (N) and autoclaved seawater (A) without adding anything as a control. The numbers of total and growing bacterial cells, protease activity, and transition of P. aeruginosa proteins were monitored in the four microcosms. Changes in the numbers of total and growing bacterial cells and protease activities indicated that bacterial detritus significantly stimulated the microbial community in the microcosms. Both the surviving P. aeruginosa in A+Pa and natural microbial community in N+Pa microcosms were able to degrade and utilize P. aeruginosa detritus; however, the community in N+Pa including various microbes maintained high activity longer, indicating that diversity is an important factor in keeping the community active. Even under the very high protease activity in N+Pa, 39-kDa and 48-kDa proteins from P. aeruginosa remained in the microcosm during the entire experiment (150 days). Immunoblotting suggested the 48-kDa protein was an intact molecule of OprP, which had been detected from the dissolved fraction of natural seawater in previous studies. This result suggests that the protein molecules that had been detected from natural seawater actually had a high tolerance to microbial degradation.     

Organic nitrogen and caloric content of detritus III. Effect on growth of a deposit-feeding polychaete, Capitella capitata

Laboratory experiments showed that individual growth rate of the deposit-feeding polychaete, Capitella capitata (type 1) can be predicted by rate of organic nitrogen supply (ration) of detritus to the animals. The rate at which detritus is available to a deposit-feeder, whether by sedimentation to the bottom, or decomposition of otherwise undigestable components via microbial activity, or production rate of microbes themselves, is important and not just the concentrations of limiting substrate of different detritus sources. Even so, the portion of total caloric content of the detritus that can be utilized by a deposit-feeder—approximated by the ‘available’ caloric content—also contributes to limiting growth. However, available caloric content usually is low when nitrogen content is low, as in the case of vascular plant detritus. Trophic transfer efficiency (net production/food supplied) is a measurement of food chain transfer that is usually calculated in carbon or caloric units. If one is interested in comparing energy or carbon flow in food chains, then use of these parameters is appropriate; if one is interested in comparing the efficiencies of different species, then calculations must be made using nutritional factors limiting growth.     

海洋碎屑小生境形成演化过程中营养盐特殊迁移过程及脱氢酶活性的变化

研究了海洋碎屑小生境形成、演化过程中营养盐特殊迁移过程和脱氢酶活性的变化。结果表明,在充氧水体中同时存在硝化和反硝化过程,并有高浓度No(?)富集。脱氢酶活性在实验第4天达到最高值,在第96天和192天出现波动。碎屑聚集体表面不但有微生物群落的演替,而且存在物理化学微环境的连续变化;当碎屑表面O_2被消耗而出现氧化还原电位梯度时,电子最终受体出现更替,非平衡过程发生改变,为适应这种改变,微生物群落重新调节新陈代谢,在分叉点附近,脱氢酶活性增大。     

Bacterial production and carbon conversion based on saltmarsh plant debris

There is a well-defined succession of micro-organisms which colonize powdered leaf debris from Spartina alterniflora and Juncus roemerianus, and aged natural detrital material when these were incubated in estuarine water at temperatures near to those recorded in the habitat at the time of collection. The natural assemblage of free-living bacteria in estuarine water rapidly enters logarithmic growth, subsequently declining with the increase in numbers of bactivorous microflagellates. These are then replaced by a mixed population of ciliates, choanoflagellates, amoeboid forms and attached bacteria which form part of a complex microbial community associated with particulate debris. The rate of increase of bacterial cells (μ), in both spring and summer experiments ranged from 0·010–0·108 h^?1 whilst estimates of bacterial carbon production ranged from 1·5 to 10·1 μg C 1^?1 h^?1, values which conform well with estimates obtained from natural assemblages of marine bacteria in coastal and estuarine waters elsewhere. Although both the ease of degradation of the detrital substrate and incubation temperature are of importance, enrichment of both powdered Spartina leaf debris and aged natural detritus with inorganic nutrients evidently enhances bacterial production under experimental conditions. In addition, the amount of carbon utilized to sustain bacterial carbon production shows a significant reduction following enrichment with NH₄, NO₃ or combinations of NO₃ + PO₄. The bacterial carbon conversion efficiency (μg C incorporated into bacterial production per μg C consumed) × 100, based on powdered Spartina leaves, and aged natural detritus, is thus increased from 9–14%, to as much as 38% in nutrient enriched media. Since NH₄, NO₃ and PO₄ values are generally low in the water column, it seems likely that bacteria achieve a carbon conversion of only 9–14% on natural suspended detrital material, with the possibility of an enhanced conversion of up to 38% occurring at the sediment-water interface where ammonia regeration occurs. This suggests that suspended bacteria which characterize estuarine waters of salt marsh areas may be responsible for the oxidation of 86–91% of the carbon which enters water column microheterotroph food chains, and are probably implicated in the large CO₂ fluxes recently recorded from coastal wetland habitats.     

Food web flows through a sub-arctic deep-sea benthic community

The benthic food web of the deep Faroe–Shetland Channel (FSC) was modelled by using the linear inverse modelling methodology. The reconstruction of carbon pathways by inverse analysis was based on benthic oxygen uptake rates, biomass data and transfer of labile carbon through the food web as revealed by a pulse-chase experiment. Carbon deposition was estimated at 2.2 mmol C m⁻² d⁻¹. Approximately 69% of the deposited carbon was respired by the benthic community with bacteria being responsible for 70% of the total respiration. The major fraction of the labile detritus flux was recycled within the microbial loop leaving merely 2% of the deposited labile phytodetritus available for metazoan consumption. Bacteria assimilated carbon at high efficiency (0.55) but only 24% of bacterial production was grazed by metazoans; the remaining returned to the dissolved organic matter pool due to viral lysis. Refractory detritus was the basal food resource for nematodes covering ∼99% of their carbon requirements. On the contrary, macrofauna seemed to obtain the major part of their metabolic needs from bacteria (49% of macrofaunal consumption). Labile detritus transfer was well-constrained, based on the data from the pulse-chase experiment, but appeared to be of limited importance to the diet of the examined benthic organisms (<1% and 5% of carbon requirements of nematodes and macrofauna respectively). Predation on nematodes was generally low with the exception of sub-surface deposit-feeding polychaetes that obtained 35% of their energy requirements from nematode ingestion. Carnivorous polychaetes also covered 35% of their carbon demand through predation although the preferred prey, in this case, was other macrofaunal animals rather than nematodes. Bacteria and detritus contributed 53% and 12% to the total carbon ingestion of carnivorous polychaetes suggesting a high degree of omnivory among higher consumers in the FSC benthic food web. Overall, this study provided a unique insight into the functioning of a deep-sea benthic community and demonstrated how conventional data can be exploited further when combined with state-of-the-art modelling approaches.     

水产品鲐鱼(Pneumatophorus japonicus)细菌多样性及优势微生物分析

为研究鲐鱼(Pneumatophorus japonicus)在不同冻藏时期的优势微生物,并且得到一个较全面的细菌群落组成结构,采用16SrDNA基因克隆文库及克隆子分析等方法,分别对冻藏1d、8d和20d条件下鲐鱼鳃体系中的细菌种群多样性、优势微生物及其中产组胺菌的变化进行分析。结果表明,不同时期鲐鱼鳃内的细菌多样性均较强;冻藏1天的鳃体系中不动杆菌属(Acinetobacter)占优势为总数的77.5%,产组胺细菌如泛菌属(Pantoea)和肠杆菌属(Enterobacter)较少;第8天优势细菌种群是梭杆菌属(Fusobacteria bacterium)和希瓦氏菌属(Shewanella),而产组胺菌如发光杆菌属(Photobacterium)和弧菌属(Vibrio)较前期数量有所增加;冻藏到第20天的优势种群为哈夫尼菌属(Hafnia)和沙雷菌属(Serratia),它们均是产组胺的菌群。鲐鱼中细菌多样性及其优势微生物的变化等全面信息可为了解鲐鱼水产品组胺发生的微生物机制及其控制方法提供重要依据。     

Studies of a mangrove basin,Tuff Crater,New Zealand: III. The flux of organic and inorganic particulate matter

Water samples were collected at 15 min intervals over 11 tidal cycles from a tidal creek draining the mangrove-covered basin of Tuff Crater, Auckland, New Zealand. The samples were filtered and total suspended sediment (TSS), inorganic suspended sediment (ISS) and organic suspended sediment (OSS) were determined. Variation in TSS was high, the concentration varied over a tidal cycle and during over-bank flows concentrations were lowest at or near slack high water. Covariance between TSS concentrations and velocity and discharge meant that the calculation of particulate matter flux over tidal hemicycles was particularly dependent on the method of estimating tidal flux. The hypsometrically-based volumetric method was found to be inappropriate, predicting a positive budget (import) more often than observed. Instead particulate matter budgets were calculated by means of the velocity-area method and indicate a net export of TSS, ISS and OSS. Floating macrodetritus was observed on both the flood and ebb tides, but a net export was found on the two tides monitored. It is considered that on an annual basis floating macrodetritus export accounts for less than 2% of the detrital production in the basin, and organic suspended sediment export from the basin is less than 3 kg C ha^?1 day^?1 and is below the rate of detrital production. It is implied that a proportion of the organic detritus produced in this basin is degraded and recycled in situ.     

东印度洋细菌类群水平与垂直分布初探

作为海洋食物网的重要组成部分,微生物在海洋的生物化学循环以及能量和元素流动中起着重要的作用。目前对东印度洋中微生物的种群结构和分布知之甚少。本研究运用分子生物学手段,包括多聚酶链式反应-变形梯度凝胶电泳(PCR-DGGE)技术和高通量测序技术,对东印度洋的赤道区域以及邻近的孟加拉湾区域水体中细菌的16S rRNA基因进行了探索。结果表明,Bacteroidetes, Proteobacteria (Alpha和Gamma类群), Actinobacteria, Cyanobacteria和Planctomycetes为研究区域微生物的主要类群。通过PCR-DGGE,发现微生物类群具有显著的水平分布模式;进一步的高通量测序的结果更加清晰的显示出细菌类群的垂直分布模式:相对其他两层,Cyanobacteria和Actinobacteria在25米水层出现更多;Bacteroidetes在25m和150m为主要类群,而在75m水层相对较少;Proteobacteria (主要为Alphaproteobacteria)类群在75m水层为优势类群。随着水层的加深,不同站位的细菌类群组成趋于一致。结果表明高通量测序能够把占据微小部分的微生物类群区分出来。本研究是针对东印度洋水体中细菌的水平和垂直分布以及多样性信息的首次报道,研究结果对于进一步发现潜在微生物功能类群以及探索这些微生物在东印度洋中的能量和物质循环中的作用有所帮助。     

The effect of a natural water-movement related disturbance on the structure of meiofauna and macrofauna communities in the intertidal sand flat of Rocas Atoll (NE, Brazil)

Rocas, the only atoll in the South Atlantic, is located 266 km off the northeast Brazilian coast. Spatial patterns in community structure of meiofauna, particularly nematodes, and macrofauna were examined along a transect through the sediment path from windward to leeward of the Rocas Atoll sand flat. Differences in benthic community structure between four zones of the sand flat were found to be significant and related to the major local processes of carbonate-grain transport and sedimentation. Both meiobenthic and macrobenthic assemblages were significantly more diverse and abundant within the sediment inflow zone (the initial part of the detrital path of Rocas sand flat) than in the other zones, where a clear impoverishment of benthic invertebrates occurred. This first study of the benthos of an intertidal sand flat over a reef island in the Atlantic showed that the meiofauna is numerically dominated by the nematodes Metoncholainussp. 1 (Oncholaimidae) and Epsilonema sp. 1 (Epsilonematidade), whilst the macrofauna is largely dominated by oligochaetes and large Oncholaimidae nematodes. Analysis of the species composition, trophic structure and abundance of both the meiobenthos and the macrobenthos revealed an impoverished community subjected to an intense water-movement disturbance.     

南海北部自由生活海洋线虫的群落结构和生物多样性

A quantitative study on the community structure and biodiversity of free-living marine nematodes and their relationship with environmental factors in the northern South China Sea were carried out based...     

Decomposition rate and invertebrate colonization of seagrass detritus along a hydrodynamic gradient in a Mediterranean coastal basin: The Stagnone di Marsala (Italy) case study

Seagrass leaf litter decomposition is a key component of marine carbon flow driven by both biotic and abiotic factors, including water movement. In this study, we analyse Posidonia oceanica litter decomposition and invertebrate colonization in three sites with different hydrodynamics in a coastal basin. Litterbags were put on the sea bed along a gradient of distance from the open sea, implying a different level of water exchange. Leaf litter mass loss and carbon and nitrogen concentration were analysed, and density and biomass of benthic invertebrates colonizing litterbags were recorded after 3, 7, 14, 47, 101, 152 and 221 days. Results showed that in the most sheltered site, the leaf litter decomposition rate, the invertebrate density and biomass and the detrital carbon release were the lowest. The reduction of the decomposition rates of seagrass leaves in the site characterized by low hydrodynamic forces may promote organic matter burial and carbon stocks, emphasizing the role of coastal basins such as ponds and lagoons as sinks of carbon and the important role of seagrass detritus in the Blue Carbon global balance.     

Food web analysis in two permanently open temperate estuaries: consequences of saltmarsh loss?

Saltmarsh vegetation, seston and microphytobenthos are all conspicuous components of most temperate estuaries and they potentially contribute to the estuarine food chain. Yet their relative contributions are unclear, as is the significance of saltmarsh losses through natural and human-induced impacts. This study aimed to quantitatively determine the contribution of various types of primary producers to detritus in the Walpole-Nornalup Estuary and Leschenault Inlet, two permanently open estuaries in SW Australia, and, estimate the flow of different types of detritus to higher trophic levels, using carbon ((13)C) and nitrogen ((15)N) stable isotopes as tracers. Results of the mixing model indicated that seston, microphytobenthos and to some extent seagrass and fringing saltmarsh were the main contributors to the detrital pool in both estuaries. However, the relative contribution of different primary producers varied both within and between estuaries. The contribution of saltmarsh was higher at sites close to rivers and dense fringing vegetation, while seston, microphytobenthos and seagrass dominated the detrital material at other sites. Benthic harpacticoid copepods were shown to feed on detritus though they appeared to actively select for different components of the detritus depending on site and estuary. Isotopic signatures of other consumers indicated that fish and invertebrates derived nutrients from MPB and detritus, either directly as food or indirectly through feeding on invertebrates. The overall contribution of saltmarsh to detritus was lower in Leschenault Inlet than in Walpole-Nornalup Estuary, possibly as a result of increased clearing of fringing vegetation around Leschenault Inlet. This pattern was however not reflected in harpacticoid food. Therefore, although losses of fringing saltmarsh around estuaries have the potential to significantly affect estuarine food webs, the significance of such losses will be site- and estuary-dependent.     

Elemental composition of individual pico- and nano-sized marine detrital particles in the northwestern Mediterranean Sea

The elemental composition of individual < 10 μm detrital particles from Mediterranean surface waters was analysed using a Transmission Electron Microscope (TEM) equipped with an energy dispersive X-Ray microanalyser. Results show that carbon and phosphorus content per detritus volume are much higher in pico-detrital particles < 2 μm (42 kg C m⁻³ and 1 kg P m⁻³) than in 5–10 μm detrital particles (20 kg C m⁻³ and 0.1 kg P m⁻³). The C:N:P atomic ratios for different sized fractions of the detrital particles were found to be 82:10:1 for < 2 μm particles, 120:29:1 for 2–5 μm particles and 308:37:1 for 5–10 μm particles. The average ratio for all size classes of detrital particles (< 10 μm) was 132:23:1. The differences in elementary compositions of the detrital particles studied here suggest that the different size fractions probably have different origins. The role and origins of < 10 μm detrital particles within the biogeochemical cycles are discussed.     

厦门湾水体中颗粒有机碳的垂向输出通量:234Th/238U不平衡的应用

对厦门湾塔角附近海域某站位叶绿素 a、POC、初级生产力、234Th/238U不平衡进行的周日变化研究表明,POC含量介于14.4～34.6 mmol/m3之间,其中碎屑有机碳与活体有机碳所占份额分别为74%～92%和8%～26%.POC垂直分布呈现由表及底降低的趋势,且白昼期间POC含量高于晚间,说明研究海域POC含量与生物过程具有密切联系.初级生产力水平在1d之中变化达5倍,垂直分布亦随深度增加而降低,与叶绿素a的变化相对应.短时间(2h)培养获得的初级生产力水平明显高于长时间培养(24 h)的结果,证实部分新固定的碳被优先呼吸排出.结合234Th/238U不平衡法获得的颗粒态234Th输出通量及输出界面颗粒物中的POC/P_Th比值,可计算出真光层 POC的垂向输出通量为16.0mmol/(m2·d),其中碎屑有机碳与活体有机碳贡献的数量分别为13.3和2.7mmol/(m2·d).POC输出通量与初级生产力的比值(ThE比值)平均为0.31,真光层POC停留时间平均为11d.上述结果与Aksnes和Wassmann[1]的模型计算结果相吻合,但与其他大多数模型的结果仍存在一定的差异.     

Croissance de juvéniles de Nereis diversicolor nourris avec des détritus d’halophytes

The comparative effect of the uptake of fresh and degraded detritus of halophytic plants, harvested from salt marches of the Mont Saint-Michel Bay (France), on the growth of a juvenile population of the annelid polychaete N. diversicolor (L.) was studied under experimental conditions in summer 1993. Fresh and degraded detritus of Spartina anglica, Halimione portulacoides and Salicornia europeae, as well as the green algae Enteromorpha sp. were distributed separately to homogenous set of juveniles for a 75 d period. The highest growth rate was obtained for worms fed with Enteromorpha sp. Administration of fresh detritus of a given halophyte species to N. diversicolor juveniles always leads to a significantly higher growth rate than did degraded detritus. This is probably due to a great microbial biomass occurring on the fresh detritus, which is moreover, much better assimilated than the detritus they colonize.     

海草凋落叶的溶解有机物的释放及其生物地球化学意义

Dissolved organic matter(DOM) represents a significant source of nutrients that supports the microbial-based food web in seagrass ecosystems. However, there is little information on how the various fractions of DOM from seagrass leaves contributed to the coastal biogeochemical cycles. To address this gap, we carried out a 30-day laboratory chamber experiment on tropical seagrasses Thalassia hemprichii and Enhalus acoroides. After 30 days of incubation, on average 22% carbon(C), 70% nitrogen(N) and 38% phosphorus(P) of these two species of seagrass leaf litter was released. The average leached dissolved organic carbon(DOC), dissolved organic nitrogen(DON) and dissolved organic phosphorus(DOP) of these two species of seagrass leaf litter accounted for 55%, 95% and 65% of the total C, N and P lost, respectively. In the absence of microbes, about 75% of the total amount of DOC, monosaccharides(MCHO), DON and DOP were quickly released via leaching from both seagrass species in the first 9 days. Subsequently, little DOM was released during the remainder of the experiment. The leaching rates of DOC, DON and DOP were approximately 110, 40 and 0.70 μmol/(g·d). Leaching rates of DOM were attributed to the nonstructural carbohydrates and other labile organic matter within the seagrass leaf. Thalassia hemprichii leached more DOC, DOP and MCHO than E. acoroides. In contrast, E. acoroides leached higher concentrations of DON than T. hemprichii, with the overall leachate also having a higher DON: DOP ratio. These results indicate that there is an overall higher amount of DOM leachate from T. hemprichii than that of E. acoroides that is available to the seagrass ecosystem. According to the logarithmic model for DOM release and the in situ leaf litter production(the Xincun Bay, South China Sea), the seagrass leaf litter of these two seagrass species could release approximately 4×10~3 mol/d DOC, 1.4×10~3 mol/d DON and 25 mol/d DOP into the seawater. In addition to providing readily available nutrients for the microbial food web, the remaining particulate organic matter(POM)from the litter would also enter microbial remineralization processes. What is not remineralized from either DOM or POM fractions has potential to contribute to the permanent carbon stocks.     

Microbial ecology concerning to the degradation of nucleic acid in the marine environment

This article summarizes the author's current work on microbial degradation of nucleic acid. The aim of this work is to elucidate parts of the saprogenic process in the marine ecosystem through the study of the behavior of nucleic acid-hydrolyzing bacteria inhabiting seawater and sediments.Considerably large population of nucleic acid-hydrolyzing bacteria was found to occur in seawater and sediments. The main genera of these microbes areVibrio spp. in coastal seas, andPseudomonas spp. in the oceanic waters. As a result of microbial attack, nucleic acid components are released into seawater. The properties of extracellular nuclease produced by a marineVibrio sp. are well adapted to the seawater environment; consequently this enzyme has high activity and stability in seawater. By determining nuclease activity in seawater and sediments, the intensities of nucleic acid-hydrolysisin situ were evaluated.Distribution patterns of marine bacteria are also discussed in reference to the occurrence of phytoplankton in seawater.     

基于高通量测序技术解析鲣鱼(Katsuwonus pelamis)鱼油和鱼白调控肠道菌群结构作用

本研究利用高通量测序技术分析小鼠喂食鲣鱼(Katsuwonus pelamis)鱼油和鱼白酶解液后肠道微生物的多样性、群落组成以及结构的变化,探讨高蛋白、高脂肪饮食对人类健康的影响。研究结果显示:喂食鱼油组小鼠的肠道微生物丰富且多样。在门水平上,对照组和鱼油组的优势菌门为拟杆菌门(Bacteroidetes);鱼白组的优势菌门为厚壁菌门(Firmicutes)。在科水平上,对照组和鱼油组中的优势菌科为Muribaculaceae;鱼白组中的优势菌科为毛螺菌科(Lachnospiraceae)。在属水平上,对照组和鱼油组中的优势菌属为Muribaculum;鱼白组中的优势菌为Lachnoclostridium;对照组、鱼油组和鱼白组小鼠的肠道微生物群落中瘤胃球菌属(Ruminococcus)和拟杆菌属(Bacteroides)等丰度较高。在种水平上,对照组和鱼油组中的优势菌为Muribaculum intestinale;鱼白组中的优势菌为解糖梭菌(Clostridium saccharolyticum)。研究结果证明鲣鱼鱼油和鱼白可以调节菌群结构和组成,增加肠道有益菌,减少病原菌的丰度等。     

Microbial colonisation of artificial and deep‐sea sediments in the Arctic Ocean

Although environmental factors such as grain size and organic carbon content may influence the distribution of microbes in marine sediments, there has been little experimental study of the topic to date. To investigate how those sediment variables affect microbial colonisation under in situ conditions, deep‐sea sediments and artificial sediments (glass beads, sands) were incubated in the Arctic deep sea at 2500 m water depth with or without chitin, one of the most important carbon polymers in marine environments. Microbial abundance, biomass, chitobiase activity and changes in community structure were monitored after 7 days and 1 year. In control sediments without chitin addition, no significant changes in microbial abundance, biomass and activity were observed after 1 year. In the presence of chitin, however, considerable increases in these parameters were recorded in all three sediment types tested. Regardless of chitin addition, natural deep‐sea sediments were always associated with higher values of microbial abundance, biomass and activity compared with artificial sediments. Sediment type was always found to be the most significant factor explaining variation in enzymatic activity and bacterial community structure as compared to the effects of chitin amount, incubation time, and changes in cell number or biomass. Overall, this is the first in situ study that has addressed the effects of multiple factors and their interactions on abundance, biomass, activity and community structure of microbial communities in the deep Arctic Ocean.     

胶州湾围隔浮游生态系统氮、磷营养盐迁移-转化模型研究

通过对目前生态动力学模型的总结和综合,以生态系统中氮、磷营养盐循环为主线,建立了适用于海洋围隔浮游生态系统的多变量的营养盐迁移-转化动力学模型.该模型包括浮游植物、浮游动物、溶解无机态营养盐、溶解有机态营养盐和生物碎屑5个模块,涉及溶解无机氮、磷酸盐、溶解有机氮、溶解有机磷、浮游植物、浮游动物和生物碎屑7个状态变量.分别利用1999年秋季和2000年夏季胶州湾围隔生态实验数据进行了模型和验证工作,成功地模拟了富加营养盐条件下围隔浮游生态系统中氮、磷营养盐生物化学迁移-转化过程,并确定了20余个参数的量值.