Short-term variations in the abundance and cell volume of bacterioplankton in an artificial tropical lake

Circadian and spatial fluctuations in bacterioplankton abundance and cell volume were examined, for the first time, in the Municipal Lake located in the down town area of Yaoundé (Capital of Cameroon, Central Africa, ca 3° 52′ N, 11° 31′ E). Bacterial cell volumes (range, 0.05 to 0.2 μm3) were consistent with those reported for other aquatic systems while bacterial densities (0.8 to 2 × 108 cells ml-1) were among the highest values reported in pelagic systems. These variables and chlorophyll a and dissolved oxygen concentrations within a single depth-zone varied from 13 to 61%, while water temperature fluctuated only from 2 to 6%. Spatial fluctuations of physical-chemical and biological variables were generally higher during the day-time than during the night-time. A significant diel variation was provided for bacterial cell volume in the surface waters where synchronized cell division was occurring during the night. The measured bacterial abundances in this study were 4 to 17 fold higher than values known from other lakes of similar trophic status, and both cell abundance and volume were not correlated with chlorophyll. We conclude that this was due to the dependence of bacterial populations to different sources of allochthonous substrates, including untreated sewage from the major influents of the lake, resuspension of benthic material, and substrate releasing from macrophytes which are prevalent in the littoral zone of the lake. This revised version was published online in September 2006 with corrections to the Cover Date.     

Dynamic of phytoplankton size-class and photosynthetic activity in a tropical hypereutrophic lake: the Yaounde municipal lake (Cameroon)

This study carried out within the framework of a multi-disciplinary project, aimed at highlighting the fundamental processes governing the functioning of the hypertrophic Yaoundé Municipal Lake. It was based on the hypothesis that, even within a small range of lake trophic status, important variations can occur in the species composition, biomass and photosynthetic activity of the phytoplankton size-fractions. For this purpose, samples were taken at weekly intervals from November 1996 to December 1997 at a fixed set of depths in the water column. Spatial-temporal fluctuations of some physical–chemical variables, associated with biological variables such as phytoplankton size-class species composition, phytoplankton size-class biomass, phytoplankton primary production and chlorophyll-a were analysed. The water transparency was low and rarely exceeded 100 cm. Conductivity values relatively higher increased generally from the top to the lake bottom. The oxygen deficiency, and sometimes anoxia, recorded from 2.5 m depth resulted in high quantities of ammonium nitrogen. Total phosphorus and total Kjeldahl nitrogen concentrations were characteristics of hypertrophic lakes. The fertility of this biotope favoured the development of a high phytoplanktonic community with remarkable physiological adaptations to the variations of the nutritive potentials of the lake, characterized by the size-structure of these organisms. Cells of small size (<12 μm) contributed up to 11.42% of the total phytoplanktonic biomass. Species with average size (12–45 μm), dominated by Chlamydomonas spp., represented a more significant contribution reaching up to 69.85%, whereas the cells of big size (>45 μm), mainly Euglenophyta, maintained the relatively most important biomass, accounting for up to 89.85% of the total phytoplanktonic biomass. Chlorophyll-a concentrations are among the highest reported for both fresh water and sea water, being a consequence of high proportions of Chlorophyta and Euglenophyta. This led to intense phytoplanktonic photosynthetic activity which continued throughout the year, even though it was confined to the upmost first meter of the water column. Analyses pointed out the allogenic nature of the functioning of this urban lake ecosystem, due to a poor waste management on the surrounding landscape. Handling editor: J. Padisak     

Biogenesis, structure, and immune-suppressive effects of virus-like particles of a Drosophila parasitoid, Leptopilina victoriae

Drosophila melanogaster larvae are attacked by virulent strains of parasitoid wasps. Females of Leptopilina heterotoma produce virus-like particles (VLPs) that efficiently destroy lamellocytes, a major larval immune effector cell type. We report here that L. victoriae, a closely related wasp species, also produces VLPs that trigger immune suppression responses in fly hosts. We compare the ability of immune suppression of the two parasitoids using a mutant host strain hopscotch^{Tumorous-lethal} (hop^Tum-l). hop^Tum-l larvae have two defects of hematopoietic origin: overproliferation of hemocytes and constitutive encapsulation of self-tissue by lamellocytes. The encapsulation phenotype is suppressed weakly by L. victoriae and strongly by L. heterotoma. In vitro studies on hop^Tum-l lamellocytes show that VLP-containing fluid from either wasp species induces lamellocyte lysis, but with different kinetics.Previously undocumented precursors of L. victoriae VLPs are synthesized in the long gland and are first visible within canals connecting secretory cells to the long gland lumen. VLP assembly occurs in the lumen. VLPs show multiple electron-dense projections surrounding a central core. Maturing particles appear segmented, singly or in arrays, embedded in the reservoir matrix. In sections, mature particles are pentagonal or hexagonal; the polygon vertices extending into spikes. Our results suggest that L. victoriae is likely to promote immune suppression by an active mechanism that is mediated by VLPs, similar to that used by L. heterotoma.     

Double-stranded RNA and virus-like particles in the edible basidiomycete Flammulina velutipes (Enokitake)

One of the commercial strains of Flammulina velutipes was analyzed for the presence of double-stranded RNA (dsRNA) elements to examine the underlying mechanism of strain degeneration. As a result, two dsRNA elements sized 1.9 and 1.8 kb were detected in mycelium derived from spontaneously brown-colored fruit body. They were not detected in the normal strains or in fruiting-impaired degenerative isolates. The dsRNAs were not in the nuclear or mitochondrial fractions, but were located in the cytoplasmic fraction. The presence of virus-like particles of ca. 50 nm diameter associated with the dsRNAs was confirmed by electron microscopic observation.     

Abundance and production of bacteria, and relationship to phytoplankton production, in a large tropical lake (Lake Tanganyika)

1. Abundance and bacterial production (BP) of heterotrophic bacteria (HBact) were measured in the north and south basins of Lake Tanganyika, East Africa, during seasonal sampling series between 2002 and 2007. The major objective of the study was to assess whether BP can supplement phytoplankton particulate primary production (particulate PP) in the pelagic waters, and whether BP and particulate PP are related in this large lake. HBact were enumerated in the 0–100 m surface layer by epifluorescence microscopy and flow cytometry; BP was quantified using ³H‐thymidine incorporation, usually in three mixolimnion layers (0–40, 40–60 and 60–100 m). 2. Flow cytometry allowed three subpopulations to be distinguished: low nucleic acid content bacteria (LNA), high nucleic acid content bacteria (HNA) and Synechococcus‐like picocyanobacteria (PCya). The proportion of HNA was on average 67% of total bacterial abundance, and tended to increase with depth. HBact abundance was between 1.2 × 10⁵ and 4.8 × 10⁶ cells mL⁻¹, and was maximal in the 0–40 m layer (i.e. roughly, the euphotic layer). Using a single conversion factor of 15 fg C cell⁻¹, estimated from biovolume measurements, average HBact biomass (integrated over a 100‐m water column depth) was 1.89 ± 1.05 g C m⁻². 3. Significant differences in BP appeared between seasons, especially in the south basin. The range of BP integrated over the 0–100 m layer was 93–735 mg C m⁻² day⁻¹, and overlapped with the range of particulate PP (150–1687 mg C m⁻² day⁻¹) measured in the same period of time at the same sites. 4. Depth‐integrated BP was significantly correlated to particulate PP and chlorophyll‐a, and BP in the euphotic layer was on average 25% of PP. 5. These results suggest that HBact contribute substantially to the particulate organic carbon available to consumers in Lake Tanganyika, and that BP may be sustained by phytoplankton‐derived organic carbon in the pelagic waters.     

横岗水库后生浮游动物群落特征

横岗水库位于广东省东莞市,是一个富营养化水体,于2005年5月和11月对该水库后生浮游动物进行采样。该水库浮游动物具有种类少、丰度低的特点,在组成上以轮虫为主。两次采样共检到25种,其中枝角类4种,成体桡足类4种,轮虫17种。5月份,共检到15种,11月份有所增加,为20种。轮虫是主要的优势类群,5月份和11月份轮虫的平均相对丰度分别为82.8%和78.8%,以裂足臂尾轮虫、萼花臂尾轮虫和前节晶囊轮虫为主要优势种。其次是桡足类,5月份和11月份平均相对丰度分别为16.6%和19.9%,以无节幼体和桡足幼体为主,成体以舌状叶镖水蚤为优势种。枝角类相对丰度最低,5月份和11月份平均相对丰度分别仅0.6%和1.3%,以微型裸腹溞为优势种类·浮蝣动物的组成、丰度和生物量均存在时间和空间上的异质性。5月份浮游动物平均丰度为242.6ind.·L^-1,平均生物量为0.912mg·L^-1,11月份浮游动物平均丰度为138.5ind.·L^-1,平均生物量为0.317mg·L^-1。从河流区到大坝区,浮游动物的丰度和生物量呈下降趋势,体现了水库中由水文和水动力学调节的浮游生物分布空间异质性。横岗水库中大个体的前节晶囊轮虫丰度较高,致使浮游动物生物量要高于浮游动物丰度相当的热带富营养化湖泊-星湖,但无论是生物量还是丰度要远低于温带富营养化湖泊。     

Equine papillomavirus type 1: complete nucleotide sequence and characterization of recombinant virus-like particles composed of the EcPV-1 L1 major capsid protein

Equus caballus papillomavirus type 1 (EcPV-1) was isolated from a cutaneous papilloma, the most common neoplasm in horses. The complete EcPV-1 nucleotide sequence and genomic organization were determined. Phylogenetic analysis showed that EcPV-1 is a close-to-root papillomavirus, with only distant relationships to the fibropapillomaviruses and the benign cutaneous papillomaviruses. To produce EcPV-1 virus-like particles (VLPs), the EcPV-1 L1 major capsid protein was expressed in insect cells using a recombinant baculovirus vector. The self-assembled EcPV-1 VLPs were morphologically indistinguishable from wild type papillomavirus virions. Monoclonal antibodies were developed against intact and denatured EcPV-1 VLPs. When tested by ELISA, all monoclonal antibodies produced against intact (#18) and some against denatured EcPV-1 VLPs (#16) reacted with intact EcPV-1 VLPs only, demonstrating that the VLPs carry type-specific conformational as well as linear epitopes on their surface. Recombinant EcPV-1 VLPs offer the potential of a noninfectious vaccine to prevent and eradicate equine cutaneous papillomatosis.     

The virus-like particles of a braconid endoparasitoid wasp, Meteorus pulchricornis, inhibit hemocyte spreading in its noctuid host, Pseudaletia separata

We previously reported that the virus-like particles of Meteorus pulchricornis (MpVLPs) are capable of inducing apoptosis by around 6h in the hemocytes of the host, Pseudaletia separata [Suzuki, M., Tanaka, T., 2006. Virus-like particles in venom of Meteorus pulchricornis induce host hemocyte apoptosis. Journal of Insect Physiology 52, 602-611], thereby protecting the oviposited egg. In the present study, we focused on analyses of the earlier events caused by the MpVLPs upon the host immune response, namely their effects on hemocyte spreading. After recognition and attachment on foreign substance, the granulocytes and plasmatocytes assemble focal complexes and focal adhesions and spread by protruding filopodia/lamellipodia. The well-spread, cultured hemocytes were subjected to MpVLPs exposure, and the morphological changes were observed. The granulocytes lost the focal complexes/adhesions visualized as phosphotyrosine clusters and retracted the filopodia/lamellipodia within 30min after exposure, while the plasmatocytes exhibited similar but distinct responses. The two hemocyte species prepared from either parasitized or MpVLP-injected hosts lost the ability to form both filopodia/lamellipodia and phosphotyrosine clusters. A caspase inhibitor, Z-VAD-FMK, did not affect these MpVLP-induced morphological changes, indicating that these earlier changes found in the hemocytes precede apoptosis. The present study together with our previous data has established that the attenuation of host immune defense by the MpVLPs comprises at least two temporally distinguishable phases: immediate and early inhibition of hemocyte spreading and the eventual induction of hemocyte apoptosis.     

Production of submerged aquatic plant communities of Doodhadhari lake Raipur, (M.P. India)

The biomass of submerged aquatic plant communities was studied periodically during two annual growth periods. Najas minor contributed 78% to the total standing biomass. Ceratophyllum demersum, Hydrilla, Nelumbo nucifera, Trapa bispinosa and Potamogeton crispus contributed towards the rest of the biomass. The production was 0.64 g./m.²/day for the growing seasons of one year.     

The microbial loop in a humic lake: seasonal and vertical variations in the structure of the different communities

Seasonal and vertical variations of the main microbial communities (heterotrophic bacteria, autotrophic picoplankton, auto- and heterotrophic nanoflagellates, ciliated protozoa and microalgae) and auto- and heterotrophic activities were estimated in a brown-colored humic and moderately acid lake in central France, the lake of Vassivière. The results demonstrated the dominant role of light in the vertical distribution of autotrophic and mixotrophic microorganisms which are confined to the 0–5 m layer during thermal stratification. The bacterial biomass was high throughout the water column probably because of the great availability of dissolved organic matter. Consequently, the predatory microzooplankton and particularly the various trophic groups of ciliated protozoa, were distributed in the water column according to the vertical distribution of the particular food resources (detritus, bacteria, algae). However, despite the great abundance of algae and bacteria, biomass of flagellated and ciliated protozoa was relatively weak. Most of the phytoplanktonic biomass was filamentous (Diatoms) or colonial (Cyanobacteria) and therefore almost probably difficult to ingest for algivorous microzooplankton. Regarding the low abundance of bacterivorous protozoa, the relation with the special physicochemical properties of this lake is discussed.

---

Résumé Les variabilités saisonnière et verticale de l'abondance et de la biomasse des principles communautés de la boucle microbienne (bactéries hétérotrophes, picoplancton autotrophe, protozoaires flagellés auto- et hétérotrophes, protozoaires ciliés, microalgues et microcyanobactéries), et des activités auto- et hétérotrophes, ont été étudiées dans un lac à caractère humique et modérément acide du Massif Central Français, le lac de Vassivière.Le dénombrement des communautés de microorganismes a été réalisé en microscopie inversée et à épifluorescence après mise en oeuvre des fixations et des colorations adéquates. Les activités photosynthétique, photo- et chemohétérotrophes ont été mesurées à partir de l'assimilation de NaH¹⁴CO₃ et d'un mélange d'acides aminés tritiés grâce à une technique de double marquage. Les résultats obtenus mettent en évidence le rôle prépondérant du facteur lumineux dans la répartition verticale des microorganismes autotrophes et mixotrophes, dont l'essentiel de la biomasse est confiné dans la zone 0–5 m en période de stratification, alors que la biomasse bactérienne est élevée sur l'ensemble de la colonne d'eau en raison, sans doute, de la grande disponibilité en matiére organique dissoute. Consécutivement, le microzooplancton prédateur, et notamment les différents types trophiques de protozoaires ciliés, se répartit dans la colonne d'eau selon la distribution verticale des ressources nutritives particularies. Cependant, compte-tenu de l'abondance bactérienne et algae, la biomasse des protozoaires flagellés et ciliésest relativement peu importante. Concernant les espèces algivores, l'essentiel de la biomasse phytoplanctonique est de nature filamenteuse (Diatomées) ou coloniale (Cyanobactéries) est est donc sans doute difficilement ingérable pour le microzooplancton. Enfin, les relations entre les caractéristiques physico-chimiques spécifiques de ce lac et le faible développement des protozoaires bactérivores sont discutées.

     

Soil respiration and microbial population in a tropical deciduous forest soil of Orissa, India

An investigation was carried out to estimate soil respiration rate and its relationship with microbial population in natural tropical forest soil, deforested soil and deforested-and-cultivated soil of Orissa, India. Soil respiration measurements and microbial isolation were performed following standard procedures. Monthly variation of soil respiration was observed to be governed by soil moisture. Considering respiration as a function of microbial population a regression analysis was made. The microfungal population showed positive relationship with the rate of soil respiration. The study revealed that conversion of natural forest led to a reduction of soil microbes and rate of soil respiration. Considering the importance of the microbial component in soil, we conclude that the conversion of natural forests to different land uses leads to the loss of biological stability of the soil.     

Seasonal variations of metabolically active bacteria in a hypertrophic lake (Hartbeespoort Dam,South Africa)

The number of metabolically active bacteria was measured with nalidixic acid over two annual cycles at three depths in the epilimnion of hypertrophic Hartbeespoort Dam, South Africa. Concurrent measurements were made of water temperature, DOC, phytoplankton production of dissolved (EDOC) and particulate organic carbon, chlorophyll a and the uptake of glucose (V_max). The objective was to determine the dominant factors correlated to the number of metabolically active bacteria and the relationship between active bacterial numbers and heterotrophic activity.The number of active bacteria was usually highest at the surface and ranged between 0.70 and 6.82 x 10⁶ cells ml^–1. The dominant factors correlated to the number of bacteria at the surface were water temperature (r = 0.65, n = 54, p<0.001), primary production (r = 0.53, n = 51, p<0.001) and EDOC (r = 0.37, n = 45, p = 0.005). Surface V_max for glucose ranged between 0.11 and 4.0 µgC 1^–1 h^–1 and was positively correlated to the number of active bacteria (r = 0.61, n = 53, p<0.001). The specific activity index (10^–12 µgC cell^–1 h^–1) varied between 80 and 2290 at the surface and was most strongly correlated to EDOC (r = 0.70, n = 48, p<0.001). Relationships between active bacterial numbers, water temperature, phytoplankton activity and glucose uptake were also found at two additional depths within the epilimnion. These data suggest that bacterial populations in nutrient enriched lakes contain a large number of metabolically active cells with high individual activity as a result of enhanced phytoplankton growth.     

Trophic interactions within the microbial food web in a tropical floodplain lake (Laguna Bufeos, Bolivia)

Whether the primary role of bacterioplankton is to act as "remineralizers" of nutrients or as direct nutritional source for higher trophic levels will depend on factors controlling their production and abundance. In tropical lakes, low nutrient concentration is probably the main factor limiting bacterial growth, while grazing by microzooplankton is generally assumed to be the main loss factor for bacteria. Bottom-up and top-down regulation of microbial abundance was studied in six nutrient limitation and dilution gradient-size fractionation in situ experiments. Bacteria, heterotrophic nanoflagellates (HNF), ciliates and rotifers showed relatively low densities. Predation losses of HNF and ciliates accounted for a major part of their daily production, suggesting a top-down regulation of protistan populations by rotifers. Phosphorus was found to be strongly limiting for bacterial growth, whereas no response to enrichment with Nitrogen or DOC was detected. HNF were the major grazers on bacteria (g-0.43 d(-1)), the grazing coefficient increased when ciliates were added (g- 0.80 d(-1)) but decreased when rotifers were added (g- 0.23 d(-1)) probably due to nutrient recycling or top-down control of HNF and ciliates by rotifers.     

Aspects of reproductive biology of curimba Prochilodus lacustris (Pisces,Prochilodontidae) in a tropical lake in Northeastern Brazil

This study evaluated the annual cycle of biological reproductive aspects of Prochilodus lacustris, a neotropical fish species, in Baixada Maranhense Protection Area in northeastern Brazil. Fish were collected monthly between June of 2015 and June of 2016 using gill nets. In the laboratory, 600 individuals were weighed, measured, and eviscerated to obtain biometric data and data for the microscopic and macroscopic analyses of the maturation stages of the gonads. These analyses allowed the determination of the reproductive period using biological indicators such as the gonadosomatic index and hepatosomatic index, condition factor, stomach repletion index, and spawning season. Abiotic variables were measured in situ during the samplig: temperature, pH, dissolved oxygen, and electrical conductivity. In addition, local rainfall data was also obtained. The results showed that the total body length of individuals varied from 151 to 211 mm in males, and from 142 to 239 mm in females. The sex ratio showed a predominance of females over males, and the species showed negative allometric growth. The annual variation of reproductive indicators and the frequency of individuals in advanced stages of gonadal maturation suggest that the reproductive cycle of the species occurs between November and January, with a reproductive peak in January. This reproductive peak coincides with the beginning of the region's rainy season. Although we did not do the fertility analysis, our results suggest that the species presents partitioned spawning. In conclusion, this results demonstrates that the reproduction of the investigated specie is influenced by associations between environmental variables on a seasonal scale and can be contribute to improve the understanding of the dynamics of the physiological reproductive process in lentic environments.     

Changes in spatial distribution during the life history of a tropical tree,Scaphium macropodum (Sterculiaceae) in borneo

We studied the spatial distribution of fruits and plants, mortality and growth rates ofScaphium macropodum (Sterculiaceae) in four 1-ha plots in a tropical rain forest in West Kalimantan, Indonesia. The species is a large deciduous tree and produces wind-dispersed fruits on defoliated twigs. The density of dispersed fruits on the ground decreased with increasing distance from a parent tree. The area under the parent's crown had the highest density of the fruits and the highest mortality of the seedlings immediately after germination. Consequently, the density of the established seedlings peaked 14 m from the tree which is outside its crown. Thick litter mainly from the parent tree seemed to physically prevent the seedlings' root from reaching the soil surface and caused the high mortality. Juvenile and mature trees distributed exclusively, suggesting that regeneration is the most successful outside of the crown of mature trees. Saplings under canopy shade did not grow well.Scaphium macropodum is hypothesized to require a gap for seedling growth and successful regeneration, whereas it can germinate and last under closed canopies as suppressed seedlings or saplings.     

Temporal abundance patterns of butterfly communities (Lepidoptera: Nymphalidae) in the Ecuadorian Amazonia and their relationship with climate

Tropical insects show temporal changes in their abundance and climate is one of the most influential factors. For tropical butterflies, few studies have quantified this relationship or analyzed changes in community composition and structure throughout time. Communities of butterflies attracted to rotting-carrion bait in one area of the Yasuni National Park, in Ecuadorian Amazonia were examined for these relationships. Butterfly communities in three different strata of the forest were sampled over 13 months using traps with rotten shrimp bait. In total, 9236 individuals of 208 species were collected between April 2002 and April 2003. The composition and structure of butterfly communities showed significant variation during the survey with a constant replacement of species throughout the year. Additionally, these communities had the highest species richness and abundance during the months with high temperatures and intermediate precipitation. Despite relatively low variation, temperature was the most significant climatic factor explaining differences in butterfly richness and abundance throughout the year. This significant response of butterfly communities to slight temperature variations reinforce the need of temporal studies to better predict how tropical butterfly populations will respond to predicted climate change.     

Seasonal variation in primary production of a large high altitude tropical lake (Lake Tana,Ethiopia): effects of nutrient availability and water transparency

Primary production rates, chlorophyll and phytoplankton biovolume were measured monthly from April 2003 to November 2004 in Lake Tana, a large tropical lake in the highlands of Ethiopia. The lake is characterised by low nutrient concentrations, and a low water transparency due to high silt load of the inflowing rivers during the rainy seasons (May–November) and daily resuspension of sediments in the inshore zone. The mean chlorophyll-a concentrations varied seasonally and ranged from 2.6 mg m⁻³ to 8.5 mg m⁻³ (mean: 4.5 mg m⁻³) in the offshore zone. Primary production was measured using the light–dark bottles technique. We incubated only at three depths, i.e. 0.6, 1.2 and 1.8 m. Therefore, we may have missed a substantial part of the depth production profile and probably also frequently missed P _max. Gross primary production in the openwater averaged 2.43 g O₂ m⁻² d⁻¹ and ranged between 0.03 g O₂ m⁻² d⁻¹ and 10.2 g O₂ m⁻² d⁻¹; production was significantly higher in the inshore zone. The highest production rates were observed in the post-rainy season (Oct–Nov), which coincided with a bloom of Microcystis and higher chlorophyll levels. This seasonal high production is probably caused by a relatively high nutrient availability in combination with favourable light conditions. The gross primary production rates of L. Tana are among the lowest compared with other tropical lakes. This will be partly the result of our underestimation of gross primary production by often missing P _max. Another cause is the oligotrophic nature of the lake in combination with its relatively low water transparency. The gross primary production per unit chlorophyll in the openwater zone was in the same range as in 30 other tropical lakes and reservoirs. The higher primary production in the inshore zone is probably the result of the daily water column mixing (Z _mix ≥ Z _t) in this area, enhancing nutrient recycling. A large proportion of the annual primary production is realised in one of the four seasons only. This productive post-rainy season is relatively short (2 months) and therefore efficiency of transfer of matter between the first and second trophic level of the Lake ecosystem will be poor.     

The differences of butterfly (Lepidoptera, Papilionoidea) communities in habitats with various degrees of disturbance and altitudes in tropical forests of Vietnam

A survey was conducted on the species composition, richness and abundance of Papilionoidea (excluding Lycaenidae) butterfly fauna in habitats with various degrees of disturbance and altitudes in tropical forests at Tam Dao National Park, northern Vietnam in 2001. The transect method was used to collect data in the survey. Six transects representing different habitat types at two sites, one site located at a low elevation of 200–250 m a.s.l., and the other located at a high elevation of 950–1000 m a.s.l., were chosen: three transects for each site, with a length of 500 m for each transect. A total of 3594 individuals of 127 species in 240 sets of data were recorded from various habitats. The differences in butterfly composition, species richness, abundance and diversity in different habitat types and altitudes were analyzed. The results showed significant differences of butterfly diversity among the different habitat types and between the low and high altitude sites. The butterfly diversity, species richness and species abundance in the low elevation habitats were higher than in the high elevation habitats. The highest diversity of butterflies occurred in the mixed habitats of agriculture, scrub and clearing lands of high disturbance. However, butterflies most important for conservation are associated with undisturbed or moderately disturbed forests only.     

Homogenisation of water and sediment bacterial communities in a shallow lake (lake Balihe,China)

1. Planktonic and benthic bacterial communities hold central roles in the functioning of freshwater ecosystems and mediate key ecosystem services such as primary production and nutrient remineralisation. Although it is clear that such communities vary in composition both within and between lakes, the environmental factors and processes shaping the diversity and composition of freshwater bacteria are still not fully understood.
2. In order to assess seasonal and spatial variability in lake bacterial communities and identify environmental factors underpinning biogeographical patterns, we performed a large-scale sampling campaign with paired water and sediment sample collection at 18 locations during four seasons in Lake Balihe, a subtropical shallow fish-farming lake in mid-eastern China.
3. Pelagic and benthic bacterial communities were distinctly different in terms of diversity, taxonomic composition and community structure, with Actinobacteria, Bacteroidetes, Cyanobacteria and Alphaproteobacteria dominating lake water, and Acidobacteria, Bacteroidetes, Chloroflexi, Gammaproteobacteria and Deltaproteobacteria dominating sediment. Nevertheless, these two communities had stronger spatial concordance and overlap in taxa during spring and autumn seasons. Together, the main drivers of both the spatial and temporal variations in Lake Balihe bacterial communities were identified as water temperature, turbidity, nitrogen and phosphorus availability, and thermal stratification controlled by wind-mixing and activity of the dense farmed fish populations. Notably, populations affiliated with Firmicutes, known to be abundant in fish gut microbiome, were especially abundant in the summer season and locations where high fish biomass was found, suggesting a potential link between fish gut microbiome and the pelagic bacterial communities.
4. Our findings demonstrated seasonal homogenisation of pelagic and benthic bacterial communities linked to marked shifts in a set of seasonally-driven environmental variables including water temperature and nutrient availability.

     

Nuclear localization of nucleocapsid-like particles and HCV core protein in hepatocytes of a chronically HCV-infected patient

Little is known about the life cycle of hepatitis C virus. Determination of the subcellular localization of HCV proteins may contribute to our understanding of the in vivo functions of the viral proteins. HCV core protein regulates multiple functions in host cells and it has been detected both in the cytoplasm and in the nucleus using different expression systems. In this study, nucleocapsid-like particles were observed in the nucleus of hepatocytes from a chronically HCV-infected patient. They were similar in size and shape to those of HCV core-like particles purified from recombinant Pichia pastoris cells. In addition the HCV core protein was detected not only in the cytoplasm but also in the nucleus and nucleolus of hepatocytes by immunoelectron microscopy. This is the first report showing nuclear localization of HCV core protein and nucleocapsid-like particles in hepatocytes during in vivo HCV infection.