Viruses in the plankton of the Rybinsk Reservoir

The role of autochthonous viruses in the regulation of bacterioplantkon abundance and production was studied in the Rybinsk Reservoir. During the ice-free period, the number of virus-like particles varied within the range of (11.0–57.4) × 10⁶ particles/ml. The virus to bacterioplankton abundance ratio ranged within 3.0–9.4. From 4 to 25% of bacterioplankton was infected by phages. A single infected cell contained up to 80 mature virus particles. The phage-induced bacterioplankton mortality in different parts of the reservoir constituted 3.7–41.8% (22.5% on average) of bacterioplankton daily production. Heterotrophic flagellates grazed from 7.6 to 68.8% (27.5% on average) of the daily bacterial production. Thus, along with flagellates, viruses are an important factor controlling bacterioplankton development in the reservoir.     

Distribution of viruses and their impact on bacterioplankton in mesotrophic and eutrophic reservoirs

Spatial distribution of planktonic viral particles (virioplankton) and mortality of heterotrophic bacteria caused by viral lysis were studied in the eutrophic Ivan’kovskoe and mesotrophic Uglichskoe reservoirs (the Upper Volga). During the summer peak of phytoplankton, the number of viral particles was higher in the Ivan’kovskoe Reservoir ((55.1 ± 9.5) × 10⁶ ml⁻¹ on average) than in the Uglichskoe Reservoir ((42.9 ± 5.1) × 10⁶ ml⁻¹ on average). The ratio of viral to bacterial abundances ranged from 2.5 to 7.0. The average number of mature phages in infected heterotrophic bacteria varied from 17 to 109 particles/cell. Most of the infected bacterial cells in the Ivan’kovskoe Reservoir were rod-shaped, and, in the Uglichskoe Reservoir, they were mainly vibrio-shaped. In the Ivan’kovskoe Reservoir, from 8.3 to 22.4% of planktonic bacteria were infected by phages, suggesting phage-induced mortality of bacterioplankton equal to 10.5–34.8% (19.1% on average) of the daily bacterial production. In the Uglichskoe Reservoir, from 9.4 to 33.5% of bacteria were phage-infected, suggesting phage-induced bacterial mortality of 13.7–40.2% (23.5% on average) of the daily bacterial production. The obtained results testify to an important role of autochthonous viruses in the regulation of bacterioplankton abundance and production in the reservoirs.     

The influence of viruses on bacterioplankton of the offshore and coastal parts of the Barents Sea

The viral and bacterioplankton communities of the Barents Sea were investigated using a combination of methods of electron and epifluorescence microscopy for the first time. The quantitative composition of the communities and the nature of their interactions were also determined. Our study showed that during the summer the abundance and biomass of bacterioplankton reached 0.4–4.0 × 10⁶ cells/mL and 25.09–84.21 mg/m³ in offshore waters and 0.4–1.8 × 10⁶ cells/mL and 19.63–100.19 mg/m³ in coastal waters, respectively. In both regions, the number of viruses (1.7–35.8 × 10⁶ and 14.5–32.4 × 10⁶ particles/mL) exceeded the number of bacteria by 2–31 and 13–60 times, respectively; the average viral production was 0.7510⁶ and 1.74 × 10⁶ particles/mL/day, respectively. The proportion of infected cells in the total bacterioplankton (7% on average) and virus-induced mortality of bacteria (8%) were much lower in offshore than in coastal waters (14 and 20%, respectively).     

Virus impact on heterotrophic bacterioplankton of water reservoirs

The quantitative distribution of viruses and their impact on heterotrophic bacterioplankton were studied in mesotrophic and eutrophic reservoirs of the Volga and Volga-Baltic waterway. The abundance of planktonic virus particles ranged from 9.4 × 10⁶ to 120 × 10⁶ ml⁻¹ and was from 2.5 to 9 times greater than the bacterial numbers. Production of virioplankton varied from 2.1 × 10⁶ to 132 × 10⁶ particles (ml day)⁻¹ and the population turnover time values were between 0.3 and 11.6 days. The maximum values of numbers and production of virio- and bacterioplankton were observed in the eutrophic Ivan’kovo reservoir. Distribution of the viruses in the Volga reservoirs depended to a significant degree on the number and activity of heterotrophic bacterioplankton. The infected bacteria accounted for 5.5–33.5% of the total bacterial abundance. Phages were an important factor of bacterial mortality. During July to September virus-induced bacterial mortality varied between 6.1 and 40.6% (20.2% on average) of daily bacterioplankton production.     

Viruses in bottom sediments of a Mesotrophic Reservoir (Rybinsk Reservoir,Upper Volga)

The total number and morphological and size composition of viriobenthos, number of bacteria infected by viruses, and burst size, as well as virus-induced mortality, abundance, and production of bacteriobenthos, have been estimated in bottom sediments of the Rybinsk Reservoir. The total number of viriobenthos in the reservoir varies within (1.1–10.9) × 10⁹ (on average, (5.9 ± 0.6) × 10⁹) particles/cm³; the total number of virus-to-bacteria ratio ranges within 0.2–2.1 (on average 0.9 ± 0.3). A weak positive correlation is found between the abundance of benthic viruses and the abundance and production of benthic bacteria. In most surveyed parts of the reservoir, infected benthic bacteria were not found or the portion of visibly infected bacterial cells (FVIC) did not exceed 0.5% of the total abundance of bacteriobenthos (N _B). A comparatively high infection of bacteria by viruses was recorded in bottom sediments only at one deep-water station, where FVIC was 2.5 of N _B.     

Viruses in the plankton of the Rybinsk Reservoir

The role of autochthonous viruses in the regulation of bacterioplankton abundance and production was studied in the Rybinsk Reservoir. During the ice-free period, the number of virus-like particles varied within the range of (11.0-57.4) x 10(6) particles/ml. The virus to bacterioplankton abundance ratio ranged within 3.0-9.4. From 4 to 25% of bacterioplankton was infected by phages. A single infected cell contained up to 80 mature virus particles. The phage-induced bacterioplankton mortality in different parts of the reservoir constituted 3.7-41.8% (22.5% on average) of bacterioplankton daily production. Heterotrophic flagellates grazed from 7.6 to 68.8% (27.5% on average) of the daily bacterial production. Thus, along with flagellates, viruses are an important factor controlling bacterioplankton development in the reservoir.     

Production of Heterotrophic Bacterioplankton in a Large Meso-Eutrophic Reservoir: The Importance of Extracellular Organic Carbon Released by Phytoplankton

The spatial distribution and seasonal dynamics of heterotrophic bacterioplankton production have been studied and the value of autochthonous sources of substrates for bacteria has been evaluated in the pelagic zone of the meso-eutrophic Rybinsk Reservoir (the Upper Volga). During the vegetation period, the bacterial production ranges from 32 to 1352 (on average 444 ± 44) mg C/(m² × day). The total input of organic carbon from the processes of extracellular production of phytoplankton, viral lysis of prokaryotic cells, and feeding of protists provides 9–64% (32 ± 3% on average) of the daily carbon demand for heterotrophic bacterioplankton.     

Heterotrophic nanoflagellates in water column and bottom sediments of the Rybinsk Reservoir: Species composition,abundance, biomass and their grazing impact on bacteria

Abundance, biomass, and taxonomic composition of heterotrophic nanoflagellates (HNFs) have been determined in the water column and bottom sediments of the large lowland meso-eutrophic reservoir (Rybinsk Reservoir, Upper Volga) in summer. The role of HNFs in the consumption of the bacterial production is estimated. In the reservoir, 55 species from 15 large taxa, including 35 species from the plankton, are identified and 45 species are from benthos samples. The orders Kinetoplastida, Choanomonada, and Chrysomonadida are distinguished by the highest species diversity. Abundance and biomass of HNFs in the water column average 991 ± 326 cells/mL and 41.4 ± 14.1 mg/m³, while in the bottom sediments they are (236 ± 61) × 10³ cells/mL and 10.7 ± 4.0 μg/mL, respectively. The biomass of HNFs average 11.2% of the bacterial biomass in the water column and only 0.8% of that in the sediments. Flagellates are found to be a major factor which control the development of bacterioplankton grazing, on average, 32.3% of its daily production, whereas their impact on bacteriobenthos is insignificant, as they consume, on average, only 2.0% of its production.     

Heterotrophic microorganisms and viruses in the water of the Gorky reservoir during a period of anomalously high water temperature

During the anomalously hot summer of 2010, the water temperature in the Gorky reservoir reached 27–33°C. Pronounced cyanobacterial blooms occurred in the limnetic part of the reservoir. The average values for bacterioplankton abundance (11.58 ± 1.25 × 10⁶ cell/mL), biomass (886 ± 96 mg/m³), and production [169 ± 32 mg C/(m³ day)] were twice as high as in the year with temperatures comparable to long-term average values. These parameters were higher in the limnetic part than in the river one. The abundance (4.86 ± 0.75 × 10³ cell/mL) and biomass (138 ± 9 mg/m³) of heterotrophic nanoflagellates were 2.3 and 1.7 times higher, respectively, than in years with regular temperature regimes. The average number of plank-tonic viral particles (N _v) in 2010 was 48.89 ± 9.54 × 10⁶ particles/mL, while virus-induced bacterial mortality (VMB) accounted for 26.9 ± 4.6% of the bacterial production. The N _v and VMB values in the limnetic part of the reservoir were, respectively, 1.5 and 1.8 times higher than in the river one.     

Trophic relationships between planktonic bacteria,heterotrophic nanoflagellates and viruses in a mesoeutrophic reservoir

The abundance, biomass, and production (Р _В) of bacrerioplankton; the taxonomic composition, abundance, biomass of heterotrophic nanoflagellates (HNF) and the rate of consumption of bacteria by HNFs; and the abundance of virioplankton, frequency of visibly infected bacterial cells, virus-induced mortality of bacterioplankton, and viral production were estimated in the mesoeutrophic Rybinsk Reservoir. The rate of bacterial mortality due to viral lysis (7.8–34.1%, on average 17.2 ± 2.0% of daily Р _В) was lower than the consumption of bacteria by the HNF community (15.4–61.3%, on average 32.0 ± 4.2% of daily Р _В). While consuming bacteria, HNFs simultaneously absorbed a significant number of viruses residing on the surface and inside the bacterial cells.     

Heterotrophic organisms and viruses in the Oka River and Cheboksary Reservoir during the abnormally hot summer of 2010

In July 2010, abnormally high water temperature (25–29°C), as well as increased biomass and phytoplankton production caused intensive development of heterotrophic bacteria and heterotrophic nanoflagellates. It was found that the abundance, biomass, and production of heterotrophic bacterioplankton, as well as the abundance and biomass of heterotrophic nanoflagellates, and the number of planktonic viruses, which were calculated on average for the reservoir under study, turned out to be higher in the years with lower water temperature (20–23°C). The virus-induced mortality of bacterioplankton in the Oka River and the Cheboksary Reservoir averaged 25.4 ± 3.4 and 22.4 ± 2.7% of the daily bacterioplankton production.     

Virio- and bacterioplankton of a small river: Influence that viruses have on the mortality of heterotrophic bacteria

The spatial distribution of virio- and bacterioplankton and the role that viruses play in heterotrophic bacteria elimination was studied in the small Il’d’ River (Rybinskoe Reservoir tributary, Upper Volga). The bacterioplankton abundance and biomass constituted 3.3–19.6 (8.5 on average) million cells/ml and 501–2353 mg/m³ (1054 mg/m³ on average), respectively. The highest abundance was registered for the shallow areas under anthropogenic and zoogenic load. The virus abundance varied from 7.4 to 66.9 million particles/ml, being 30.9 million particles/ml on average. The bacteria: virus ratio was in the range of 1.2–11.0 (4.0 on average); the maximal values were registered for the deepest parts of the river. One infected bacterial cell carried up to 45 virile phages. The virus-induced mortality (VIM) was in the range of 1.1–7.8% (3.7% on average) from daily bacterial production. These data evidenced a high abundance of bacterioplankton in the studied river and an insignificant impact of virus-mediated regulation on bacterial abundance and production.     

深圳近海表层浮游细菌分布特征及其环境影响因素

于2015年3月、5月、8月和10月在深圳市近岸海域(珠江口、深圳湾和大亚湾)采集表层水样,利用流式细胞仪测定总浮游细菌、高DNA含量亚群细菌(HNA)、低DNA含量亚群细菌(LNA)的丰度,分析它们的时空分布特点,阐释环境因子对浮游细菌时空分布格局的影响。结果表明,珠江口、深圳湾和大亚湾海域表层浮游细菌的平均丰度依次降低,分别为3.82×10~6个/mL、7.67×10~6个/mL和3.38×10~6个/mL。珠江口海域浮游细菌丰度由远岸到近岸递增,深圳湾海域湾内各站位浮游细菌丰度差异较小,大亚湾海域浮游细菌丰度空间差异不显著(P0.05)。浮游细菌丰度时间差异主要受温度影响,空间差异主要受营养盐和叶绿素a影响。HNA亚群丰度时空差异性比LNA亚群的大,HNA亚群受温度影响显著(P0.01),而LNA亚群与温度相关性不显著(P0.05)。环境对HNA和LNA亚群丰度的影响有许多相似之处,但两者对某些环境因子有着不同的响应,说明它们在近海表层生态系统中可能扮演着部分重叠但略有不同的角色。     

Abundance,biomass, and production of heterotrophic bacteria in a large plain reservoir during the ice-covered period

The abundance, biomass, production, and size and morphological structure of heterotrophic bacteria have been determined and their contribution to the total plankton biomass has been assessed in the Rybinsk Reservoir (the Upper Volga) during the ice-covered period. Structural and functional characteristics of bacteria, except for their cell sizes in winter, are lower than those in the growing season. However, heterotrophic bacteria have made the main contribution (89.3%) to the total biomass of plankton community in winter. During the growing season, phytoplankton is a major component of plankton (48.8%), while the bacteria average 36.5%. The total plankton biomass under the ice averages 148 mg C/m³, which is 2.6 times lower than in the period of open water. During the ice-covered period, the number of protists is small and they consume an insignificant part of the bacterial production; viral lysis is the main reason for bacterial mortality.     

Seasonal Variation of Virioplankton in a Eutrophic Shallow Lake

Lake Donghu is a typical eutrophic freshwater lake in which high abundance of planktonic viruses was recently revealed. In this study, seasonal variation of planktonic viruses were observed at three different trophic sites, hypertrophic, eutrophic, and mesotrophic regions, and the correlation between their abundances and other aquatic environmental components, such as bacterioplankton, chlorophyll a, burst size, pH, dissolved oxygen, and temperature, was analyzed for the period of an year. Virioplankton abundance detected by transmission electron microscope (TEM) ranged from 5.48 × 10⁸ to 2.04 × 10⁹ ml⁻¹ in all the sites throughout the study, and the high abundances and seasonal variations of planktonic viruses were related to the trophic status at the sampled sites in Lake Donghu. Their annual mean abundances were, the highest at the hypertrophic site (1.23×10⁹ ml⁻¹), medium at the eutrophic site (1.19×10⁹ ml⁻¹), and the lowest at the mesotrophic site (1.02×10⁹ ml⁻¹). The VBR (virus-to-bacteria ratio) values were high, ranging from 49 to 56 on average at the three sampled sites. The data suggested that the high viral abundance and high VBR values might be associated with high density of phytoplankton including algae and cyanobacteria in this eutrophic shallow lake, and that planktonic viruses are important members of freshwater ecosystems.     

Structural and functional characteristics of the bacterioplankton of rivers flowing through a large city (Cherepovets,Upper Volga Region)

The structural and functional properties of the bacterioplankton in two small rivers and the Sheksna River that run through the large industrial city of Cherepovets were studied from April to October 2009–2011. The three-year average numbers and biomass of planktonic bacteria in small rivers were 18.7–18.8 million cells/mL and 3.5–4.9 g/m³, respectively; these values in the Sheksna River’s littoral zone were 15.8 million cells/mL and 2.2 g/m³. The bacterioplankton production in the small water courses exceeded that in the Sheksna River by a factor of 1.8–2.2. The contribution of bacterial filaments to the total biomass and the total bacterioplankton production increases in small polluted rivers.     

北京市五大水系水体浮游细菌的数量特征研究

为掌握水域浮游细菌数量分布特征及其变化情况,采用荧光显微镜细菌计数法（AODC）于2016年6月至2018年9月研究了北京市五大水系浮游细菌的数量特征。结果表明,各水系浮游细菌密度分别为潮白河水系（0.24～28.46）×104 cell/mL,大清河水系（1.34～64.00）×10⁴ cell/mL,永定河水系（0.17～6.77）×10⁴ cell/mL,北运河水系（0.24～64.00）×10⁴ cell/mL,蓟运河水系（0.80～112.00）×10⁴ cell/mL。SPSS相关分析表明,各水系浮游细菌密度与水体理化因子间的相关性存在明显差异,大清河水系细菌密度与TN（P<0.05）呈显著正相关,与TP（P<0.01）和ADP(P<0.01)呈极显著正相关;永定河水系细菌密度与TAN（P<0.05）和TP(P<0.05)呈显著正相关,与ADP（P<0.01）呈极显著正相关;蓟运河水系细菌密度与Chl-a（P<0.05）呈显著正相关;潮白河水系及北运河水系细菌密度则与各理化因子均无显著相关性。从浮游细菌数量来看,各水系水质均较好,其中永定河水系水质最优。     

Biofilm formation on brass coupons exposed to a cooling system of an oil refinery

Brass coupons (70% Cu 30% Zn) were exposed to a cooling freshwater system of an oil refinery, in order to investigate susceptibility of the metal to biofilm formation. The coupons were fixed on bypasses at points which allowed the circulation of makeup, cooling and return water. The number of aerobic, anaerobic and sulfate-reducing bacteria was determined in both the planktonic and the sessile phases. Maximum bacterial concentrations were detected in the cooling water, corresponding to 2.1 ± 0.1 × 10⁶ CFU ml⁻¹ (planktonic phase) and 1.3 ± 0.2 × 10⁵ CFU cm⁻² (sessile phase) for aerobic bacteria and to 3.2 ± 0.3 × 10⁵ cells ml⁻¹ (planktonic phase) and 6.2 ± 0.7 × 10⁵ cells cm⁻² (sessile phase) for anaerobic bacteria. Sulfate-reducing bacteria (SRB) were observed only in the planktonic phase, being found in greater numbers in the return water. Scanning electron microscopy (SEM) analysis indicated that biofilm formation occurred at the three monitored sites and showed a diversity in cell morphology. Nonetheless, no evidence of corrosion was observed on the brass coupons during the experimental period. Received 22 May 1997/ Accepted in revised form 19 September 1997     

一株溶藻细菌对海洋原甲藻的溶藻效应

从深圳大鹏湾南澳赤潮爆发海域的表层海水中分离得到1株对海洋原甲藻(Prorocentrum micans)具有溶藻活性的海洋细菌,菌株编号为N10。利用液相感染法研究了该溶藻细菌的溶藻效果和溶藻作用方式。结果表明,菌株N10能使藻细胞失去运动活性,并膨胀变形,细胞膜内物质聚集于一端,藻细胞最终破裂死亡。菌悬液接种到藻液中的量越大,初始细菌密度越高,其溶藻效果越强。菌悬液以1∶10的体积比接种到藻液中时,藻细胞在24 h的死亡率为83%,至72 h全部溶解死亡;体积比为1∶20的藻细胞在24 h的死亡率为71%,之后藻细胞密度略有波动,120 h时死亡率达77%;而体积比为1∶100的藻细胞密度在前24 h有所下降,死亡率达39%,之后藻细胞密度又开始明显上升;对照组的藻细胞密度均呈明显上升趋势。菌悬液过滤液和高温加热处理后的菌悬液过滤液对海洋原甲藻均无溶藻活性,表明菌株N10的溶藻方式为直接溶藻。通过16S rRNA序列分析并与GenBank数据进行同源性检索,并结合细菌形态及生理生化特征,菌株N10隶属于黄杆菌科(Flavobacteriaceae)中的Muricauda sp.。     

电解水的抑菌活性及对食品加工表面材料的消毒效果

为了考查应用电解水消除细菌污染的可行性,对氧化电解水的杀菌效果及对食品加工表面材料的消毒效果进行了研究。结果表明,含0.1%NaCl的自来水经7min的电解后所获得的氧化电解水,能在2min内将菌液浓度分别为4.20×106CFU/mL,2.18×106CFU/mL,1.44×106CFU/mL,2.10×106CFU/mL,1.94×106CFU/mL的埃希氏大肠杆菌(Escherichia coliO157:H7)、沙门氏菌(Salmonella enteritidis)、单核细胞增生李斯特菌(Listeria monocytogenes)、摩化摩根菌(Morganella morganii)、副溶血性弧菌(Vibrio parahaemolyticus)几乎全部杀死。另外,对食品加工表面接触材料中的地板砖、不锈钢板、瓷砖进行染菌消毒试验结果表明,含0.1%NaCl的电解水同样能将上述浓度的菌液感染到食品表面接触材料后在5min之内几乎全部将其杀死,是一种理想的食品表面材料消毒剂。