Influence of Bacterial Lysate Quality on Growth of Two Bacterioplankton Species

All physico-chemical parameters that affect bacterial growth rate will also affect bacterial molecular composition, which in turn influences the chemical composition of bacterial lysate and its turnover rate in the ecosystem. To produce qualitatively different lysates, Vibrio sp. cells were grown under different pH, salt, or temperature conditions in rich growth media and then washed and lysed by autoclaving. Both the absolute concentrations and the ratios between elements in the lysates varied with different growth conditions, implying differences in lysate quality. Either Pseudoalteromonas sp. or Vibrio sp. was grown on the lysates at non-limiting lysate concentrations. Different lysates supported growth rates of Pseudoalteromonas sp. in the range from 0.25 to 1.53 h⁻¹. On the other hand, growth rates of Vibrio sp. grown on its own lysates were around 0.4 h⁻¹ and were not dependent on lysate quality. Two orders of magnitude decrease in Zn concentration in Vibrio sp. cells grown on different lysates as compared to cells grown on rich growth medium suggested that Zn might be a factor limiting growth. In the simple microbial loop studied, the initial difference in lysate quality was preserved in Pseudoalteromonas sp., whereas Vibrio sp. decreased the initial differences in lysate quality, thereby neutralizing the primary effect of environmental conditions on carbon turnover.     

Purification and Partial Identification of Novel Antimicrobial Protein from Marine Bacterium <Emphasis Type="Italic">Pseudoalteromonas</Emphasis> Species Strain X153

A marine bacterium, X153, was isolated from a pebble collected at St. Anne du Portzic (France). By 16S ribosomal DNA gene sequence analysis, X153 strain was identified as a Pseudoalteromonas sp. close to P. piscicida. The crude culture of X153 was highly active against human pathogenic strains involved in dermatologic diseases, and marine bacteria including various ichthyopathogenic Vibrio strains. The active substance occurred both in bacterial cells and in culture supernatant. An antimicrobial protein was purified to homogeneity by a 4-step procedure using size-exclusion and ion-exchange chromatography. The highly purified P-153 protein is anionic, and sodium dodecylsulfate polyacrylamide gel electrophoresis gives an apparent molecular mass of 87 kDa. The X153 bacterium protected bivalve larvae against mortality, following experimental challenges with ichthyopathogenic Vibrio. Pseudoalteromonas sp. X153 may be useful in aquaculture as a probiotic bacterium.     

The Response of Vibrio- and Rhodobacter-Related Populations of the NW Mediterranean Sea to Additions of Dissolved Organic Matter, Phages, or Dilution

We investigated the growth response of the heterotrophic prokaryotic community focusing on Vibrio- and Rhodobacter-related populations (SRF3) to variation in the availability of dissolved organic matter (DOM), population density-dependent effects, and prokaryotic virus (phage) infection in coastal and offshore waters of the NW Mediterranean Sea. We tested the response of the prokaryotic community to three different DOM fractions prepared by ultrafiltration. One of the DOM fractions contained phages (<0.2 m), a second was virus-free (<100 kDa), and a third contained only low molecular weight (<1 kDa). The proportion of Vibrio and SRF3 populations as determined by fluorescent in situ hybridization in the community ranged from <1 to 6.2% and from 3.2 to 6.3%, respectively. Based on changes in cell numbers, growth rates ranged from 2.1 to 3.1 day⁻¹ for Vibrio and from 0.8 to 1.2 day⁻¹ for SRF3. Growth rates of Vibrio were similar or higher than those of the total prokaryotic community, whereas the ability of Vibrio to use high molecular weight (HMW) DOM and the responses to additions of phage-rich material were lower. Growth rates of SRF3 were lower than that of the community. Susceptibility to infection of SRF3 was sometimes lower than in the community, whereas the growth stimulation of HMW DOM was similar or lower. Reducing the cell concentrations of the prokaryotic community by dilution stimulated the overall growth of the community, including that of its constituent Vibrio and SRF3 populations, but the effect was smaller on the SRF3 and greater on Vibrio populations than for the total community. Comparisons with the community also revealed that life strategy traits of bacterial populations differed between coastal and offshore waters. Overall, our data suggest that Vibrio is an r-strategist or opportunistic population in the NW Mediterranean Sea, whereas SRF3 is a K-strategist or equilibrium population.     

Evidence of enhanced microbial activity in the interstitial space of branched corals: possible implications for coral metabolism

Water samples from the interstitial space of 4 Indo-Pacific coral species (Acropora sp., Echinopora horrida, Psammocora digita and Pavona clavus) and a Mediterranean coral (Cladocora cespitosa) were analysed for NO ₃ ^- +NO ₂ ^- , NH ₄ ⁺ , molybdate reactive phosphorus, bacterial and flagellate biomass and dissolved organic matter (DOM) and compared with ambient water concentrations. Higher values of NO ₃ ^- +NO ₂ ^- , bacterial and flagellate biomass were observed within the interstitial space of the corals. The lower DOM pool in the interstitium in combination with the high bacterial biomass suggests high bacterial activity and efficient substrate utilization, necessary to compensate for nanoflagellate predation. Since corals may be able to feed on bacteria, the high microbial biomass (bacterial and flagellate) may be utilized either directly as an additional heterotrophic food source, or indirectly in that microbes may act as attractants for microbe-feeding zooplankters, which in turn serve as food for the corals. The combined effect of reduced flow velocities between the coral branches and its associated fauna are probably the main factors in creating a specific environment more or less independent of the nutritive stage of the surrounding water.     

Determination of Total Protein Content of Bacterial Cells by SYPRO Staining and Flow Cytometry

An assay has been developed for measuring protein biomass of marine planktonic bacteria by flow cytometry. The method was calibrated by using five species of Bacteria (an Arcobacter sp., a Cytophaga sp., an Oceanospirillum sp., a Pseudoalteromonas sp., and a Vibrio sp.) recently isolated from seawater samples and grown in culture at different temperatures. The intensity of SYPRO-protein fluorescence of these bacteria strongly correlated with their total protein content, measured by the bicinchoninic acid method to be in the range of 60 to 330 fg of protein cell⁻¹ (r² = 0.93, n = 34). According to the calibration, the mean biomass of planktonic bacteria from the North Sea in August 1998 was 24 fg of protein cell⁻¹.     

Vibrio sp. DSM 14379 Pigment Production—A Competitive Advantage in the Environment?

The ability to produce several antibacterial agents greatly increases the chance of producer’s survival. In this study, red-pigmented Vibrio sp. DSM 14379 and Bacillus sp., both isolated from the same sampling volume from estuarine waters of the Northern Adriatic Sea, were grown in a co-culture. The antibacterial activity of the red pigment extract was tested on Bacillus sp. in microtiter plates. The MIC₅₀ for Bacillus sp. was estimated to be around 10⁻⁵ mg/L. The extract prepared form the nonpigmented mutant of Vibrio sp. had no antibacterial effect. The pigment production of Vibrio sp. was studied under different physicochemical conditions. There was no pigment production at high or low temperatures, high or low salt concentrations in peptone yeast extract (PYE) medium, low glucose concentration in mineral growth medium or high glucose concentration in PYE medium. This indicates that the red pigment production is a luxurious good that Vibrio sp. makes only under favorable conditions. The Malthusian fitness of Bacillus sp. in a co-culture with Vibrio sp. under optimal environmental conditions dropped from 4.0 to −7.6, which corresponds to three orders of magnitude decrease in the number of CFU relative to the monoculture. The nonpigmented mutant of Vibrio sp. in a co-culture with Bacillus sp. had a significant antibacterial activity. This result shows that studying antibacterial properties in isolation (i.e. pigment extract only) may not reveal full antibacterial potential of the bacterial strain. The red pigment is a redundant antibacterial agent of Vibrio sp.     

Rapid screening and dereplication of bacterial isolates from marine sponges of the Sula Ridge by Intact-Cell-MALDI-TOF mass spectrometry (ICM-MS)

Rapid grouping of bacterial isolates is critical in comprehensive microbial studies of environmental samples or screening programmes e.g. in unknown marine environments where large numbers of strains have to be isolated on different growth media. Sets of bacteria have been cultured from the marine sponges Isops phlegraei, Haliclona sp. 1, Phakellia ventilabrum and Plakortis sp. growing at a depth of about 300 m on the Sula Ridge close to the Norwegian coast. We employed Intact-Cell MALDI-TOF (ICM) mass spectrometry to achieve a rapid proteometric clustering of a subset of the strain collection including 456 isolates. Cluster analysis of mass spectra resolved the strains into 11 groups corresponding to species of Alteromonas (15), Bacillus (3), Colwellia (31), Erythrobacter (19), Marinobacter (14), Marinococcus (6), Pseudoalteromonas (297), Pseudomonas (56), Roseobacter (3), Sphingomonas (2) and Vibrio (10) as verified by 16 S rDNA analysis. A further discrimination into subgroups was demonstrated for different isolates from the genus Pseudoalteromonas. The approach described here permits the rapid identification of isolates for dereplication, and the selection of strains representing rare species for subsequent characterization.     

Degradation of surface-water dissolved organic matter: influences of DOM chemical characteristics and microbial populations

The degree to which biodegradation of dissolved organic matter (DOM) depends on microbial community structure and source remains unknown. In this study, we concentrated the microbial biomass from two streams in northern Michigan and a dystrophic bog lake in northern Wisconsin with varying initial DOM concentration (6.7–78.8 mg C l^–1) and DOM chemical characteristics (e.g. DOM average molecular weights from 808–1887 Da). Each of the three microbial inocula was added to each of the three DOM sources at in situ population levels for a total of nine treatments. Changes in DOM concentration and bacterial productivity, along with chemical characteristics, were examined over 308 h. The [³H]-leucine incorporation method was used to measure microbial production. In two of three sampling sites, bacterial communities were most productive when metabolizing DOM in their native waters. A variable peak in productivity was seen between 16–48 h after inoculation, followed by a drop in productivity in most treatments, with periods of DOM production most likely due to microbial turnover. These data suggest that microbial communities are better able to degrade the DOM of their native habitats, suggesting that biodegradation of DOM is influenced by source-specific microbial species and DOM chemical characteristics.     

Statistic evaluation of the influence of species variation,culture conditions,surface wettability and fluid shear on attachment and biofilm development of marine bacteria

A budding coccoid bacterium, (CH1), a Vibrio sp. and a Pseudomonas sp. were investigated for factors governing their attachment to glass surfaces in static batch culture and laminar flow continuous culture systems. An analysis of variance showed that the three species exhibited very different responses. For CH1 attachment was dependent on cell density, incubation time and nutrient concentration. The Vibrio sp. was affected by nutrient concentration while the attachment of the Pseudomonas sp. was independent of cell density, incubation time and nutrient concentration. A comparison of attachment to hydrophilic and hydrophobic surfaces showed that attachment of the Vibrio sp. and CH1 to hydrophilic surfaces was 3 and 10 times greater respectively than to hydrophobic surfaces while Pseudomonas attached in equal numbers to both surfaces. The continuous culture system with defined flow hydrodynamics and growth conditions at steady state revealed a random sampling effect 3 times smaller than the batch culture system did. When the biofilm development of Pseudomonas sp. was followed during 46 h at different fluid shear under laminar and turbulent flow conditions, the former biofilm reached 3.3·10⁸ cells·cm^-2 and the latter 8.2·10⁷ cells·cm^-2.Non-common abbreviation NSS Nine salt solution     

Impact of NH4NO3 on microbial biomass C and N and extractable DOM in raised bog peat beneath Sphagnum capillifolium and S. recurvum

Regular bi-weekly additions of NH₄NO₃, equivalent to a rate of 3 g N m^–2 yr^–1, were applied to cores of Sphagnum capillifolium, inhabiting hummocks and S. recurvum a pool and hollow colonizer, in a raisedbog in north east Scotland. Microbial biomass C and N,both measured by chloroform extraction, showed similarseasonal patterns and, for most depths, the effects ofadded N on microbial biomass C and N changed withtime. The addition of inorganic N had greatest effectduring October when the water table had risen to thesurface and microbial C and N in the untreated coreshad decreased. Microbial C and N were maintained at75 g C m^–2 and 8.3 g N m^–2 above the values in the untreated cores and far exceeded the amounts of N that had been added up to that date (1 g N m^–2) as NH₄NO₃. This increased microbial biomass was interpreted as leaching of carbonaceous material from the NH₄NO₃ treated moss resulting in greater resistance of the microbialbiomass to changes induced by the rising water table.Treatment with N also caused significant reductions inextractable dissolved organic N (DON) at 10–15 cmdepth, beneath the surface of the moss, but at lowerdepths to 25 cm no changes were observed. Extracteddissolved organic carbon (DOC) was not affected by Ntreatment and showed less seasonal variation than DON,such that the C:N ratio of dissolved organic matter(DOM) in all depths increased from approximately 4 inJuly to around 30 in December.     

Seasonal Dynamics and Modeling of a <Emphasis Type="Italic">Vibrio</Emphasis> Community in Coastal Waters of the North Sea

Vibrio species are ubiquitously distributed in marine waters all over the world. High genome plasticity due to frequent mutation, recombination, and lateral gene transfer enables Vibrio to adapt rapidly to environmental changes. The genus Vibrio comprises several human pathogens, which commonly cause outbreaks of severe diarrhea in tropical regions. In recent years, pathogenic Vibrio emerged also in coastal European waters. Little is known about factors driving the proliferation of Vibrio spp. in temperate waters such as the North Sea. In this study a quantification of Vibrio in the North Sea and their response to biotic and abiotic parameters were assessed. Between January and December 2009, Vibrio at Helgoland Roads (North Sea, Germany) were quantified using fluorescence in situ hybridization. Vibrio numbers up to 3.4 × 10⁴ cells × mL⁻¹ (2.2% of total microbial counts) were determined in summer, but their abundance was significantly lower in winter (5 × 10² cells × mL⁻¹). Correlations between Vibrio and nutrients (SiO₂, PO₄ ³⁻, DIN), Secchi depth, temperature, salinity, and chlorophyll a were calculated using Spearman rank analysis. Multiple stepwise regression analysis was carried out to analyze the additive influence of multiple factors on Vibrio. Based on these calculations, we found that high water temperature and low salinity best explained the increase of Vibrio cell numbers. Other environmental parameters, especially nutrients and chlorophyll a, also had an influence. All variables were shown to be subject to the overall seasonal dynamics at Helgoland Roads. Multiple regression models could represent an efficient and reliable tool to predict Vibrio abundances in response to the climate change in European waters.     

Antibiofilm Activity of the Marine Bacterium Pseudoalteromonas sp. Strain 3J6

Biofilm formation results in medical threats or economic losses and is therefore a major concern in a variety of domains. In two-species biofilms of marine bacteria grown under dynamic conditions, Pseudoalteromonas sp. strain 3J6 formed mixed biofilms with Bacillus sp. strain 4J6 but was largely predominant over Paracoccus sp. strain 4M6 and Vibrio sp. strain D01. The supernatant of Pseudoalteromonas sp. 3J6 liquid culture (SN_3J6) was devoid of antibacterial activity against free-living Paracoccus sp. 4M6 and Vibrio sp. D01 cells, but it impaired their ability to grow as single-species biofilms and led to higher percentages of nonviable cells in 48-h biofilms. Antibiofilm molecules of SN_3J6 were able to coat the glass surfaces used to grow biofilms and reduced bacterial attachment about 2-fold, which might partly explain the biofilm formation defect but not the loss of cell viability. SN_3J6 had a wide spectrum of activity since it affected all Gram-negative marine strains tested except other Pseudoalteromonas strains. Biofilm biovolumes of the sensitive strains were reduced 3- to 530-fold, and the percentages of nonviable cells were increased 3- to 225-fold. Interestingly, SN_3J6 also impaired biofilm formation by three strains belonging to the human-pathogenic species Pseudomonas aeruginosa, Salmonella enterica, and Escherichia coli. Such an antibiofilm activity is original and opens up a variety of applications for Pseudoalteromonas sp. 3J6 and/or its active exoproducts in biofilm prevention strategies.Biofilms are defined as microbial communities of cells that are irreversibly attached to a substratum, to an interface, or to each other and are embedded into a matrix of extracellular polymeric substances that they have produced (8). It is now considered that most (if not all) bacteria are capable of forming biofilms and that this is their predominant bacterial life-style. Biofilm formation is a complex biological phenomenon and has been generally described as a temporal process involving a succession of distinct stages: a reversible and then irreversible attachment of planktonic bacteria onto a surface, the formation of microcolonies either by the clonal growth of attached cells or by the active translocation of cells across the surface, the coalescence of growing microcolonies to form a macrocolony, and cell dispersal. It should, however, be noted that this developmental model still requires further experimental validation, especially concerning the possibility of a hierarchical order of genetic pathways (26). Furthermore, Karatan and Watnick (17) pointed out that there are as many different types of biofilms as there are bacteria and that a single bacterium may even make several different types of biofilms under different environmental conditions. Biofilm formation is associated with the virulence of pathogenic bacteria, and cells included within a biofilm are generally more resistant (up to 1,000-fold) to antibiotics and disinfectants than free-living bacteria (8, 26). Biofilms are therefore a major concern in medicine and in medical environments but also in all domains where their growth constitutes a source of contamination for humans or animals (food industry, cooling towers, and water pipes, etc.) or leads to economical losses (biofouling of boats and immersed structures and material biocorrosion, etc.). The development of antibiofilm strategies is therefore of major interest and currently constitutes an important field of investigation in which environmentally friendly antibiofilm molecules or organisms are highly valuable (5, 7, 9).Marine bacteria belonging to the genus Pseudoalteromonas of the class Gammaproteobacteria are often found in association with marine eukaryotes, and their ability to produce a variety of biological activities has attracted particular attention (2, 11, 13, 15, 28). We previously isolated marine bacteria attached to solid surfaces (glass in most cases) immersed for 3 or 6 h in the Morbihan Gulf or in the Bay of Brest, France (10, 20, 21, 27). Out of the three Pseudoalteromonas strains isolated, we were able to tag strain 3J6 with a green fluorescent protein (GFP)-encoding plasmid. This allowed us to investigate whether Pseudoalteromonas sp. strain 3J6 affected the biofilm growth of other marine bacterial isolates. Here, we report that strain 3J6 predominated in two-species biofilms over Paracoccus sp. strain 4M6 and Vibrio sp. strain D01. Although devoid of antibacterial activity against planktonic cells, Pseudoalteromonas sp. 3J6 exoproducts impaired biofilm formation by Paracoccus sp. 4M6 and Vibrio sp. D01. We characterized the effects of these exoproducts on the latter strains and on other bacteria.     

Suppression of Settlement of Larvae of Fouling Organism by Water-Soluble Substances from Epibiotic Bacteria

Twenty-nine bacterial strains were isolated from the surface of the green alga Ulva reticulata, the soft coral Dendronephthya sp., and the sponge Haliclona sp. The bacterial species Vibrio alginolyticus, Vibrio sp. 4, an unidentified α-Proteobacterium, Vibrio sp. 7, Pseudoalteromonas sp. 2, and Pseudoalteromonas sp. 4 were found to suppress the larval settlement of the polychaete Hydroides elegans (Haswell, 1883) and the bryozoan Bugula neritina (Linnaeus, 1758). Aqueous extracts of five bacteria (all those named above except Pseudoalteromonas sp. 2) prevented larval settlement. Bacteria V. alginolyticus, Vibrio sp. 4, and an unidentified α-Proteobacterium were first discovered to produce high-molecular substances (>100 kDa) preventing larval settlement. Their activity was inhibited by amylase treatment, while trypsin and papain did not influence their activity. The data obtained proved that bacteria from the surface of the number of marine organisms excrete water-soluble sacchariferous compounds preventing larval settlement.     

Response of growth and fatty acid compositions of Nannochloropsis sp. to environmental factors under elevated CO2 concentration

Nannochloropsis sp. was grown with different levels of nitrate, phosphate, salinity and temperature with CO₂ at 2,800 μl l⁻¹. Increased levels of NaNO₃ and KH₂PO₄ raised protein and polyunsaturated fatty acids (PUFAs) contents but decreased carbohydrate, total lipid and total fatty acids (TFA) contents. Nannochloropsis sp. grew well at salinities from 22 to 49 g l⁻¹, and lowering salinity enhanced TFA and PUFAs contents. TFA contents increased with the increasing temperature but PUFAs contents decreased. The highest eicosapentaenoic acid (EPA, 20:5ω3) content based on the dry mass was above 3% under low N (150 μM NaNO₃) or high N (3000 μM NaNO₃) condition. Excessive nitrate, low salinity and temperature are thus favorable factors for improving EPA yields in Nannochloropsis sp.     

Illuminating microbial species-specific effects on organic matter remineralization in marine sediments

Marine microorganisms play a fundamental role in the global carbon cycle by mediating the sequestration of organic matter in ocean waters and sediments. A better understanding of how biological factors, such as microbial community composition, influence the lability and fate of organic matter is needed. Here, we explored the extent to which organic matter remineralization is influenced by species-specific metabolic capabilities. We carried out aerobic time-series incubations of Guaymas Basin sediments to quantify the dynamics of carbon utilization by two different heterotrophic marine isolates (Vibrio splendidus 1A01; Pseudoalteromonas sp. 3D05). Continuous measurement of respiratory CO₂ production and its carbon isotopic compositions (¹³C and ¹⁴C) shows species-specific differences in the rate, quantity and type of organic matter remineralized. Each species was incubated with hydrothermally-influenced versus unimpacted sediments, resulting in a ~2-fold difference in respiratory CO₂ yield across the experiments. Genomic analysis indicated that the observed carbon utilization patterns may be attributed in part to the number of gene copies encoding for extracellular hydrolytic enzymes. Our results demonstrate that the lability and remineralization of organic matter in marine environments is not only a function of chemical composition and/or environmental conditions, but also a function of the microorganisms that are present and active.     

杉木和米槠凋落叶DOM对土壤碳矿化的影响

DOM(Dissolved organic matter)是土壤微生物呼吸的重要底物,凋落物淋溶的DOM对土壤碳矿化具有重要影响。选择中亚热带地区具有代表性的杉木(Cunninghamia lanceolata)和米槠(Castanopsis carlesii)凋落叶作为研究对象,通过两个月的短期室内培养,把不同凋落叶浸提出的DOM添加到培养瓶中,定期测定土壤碳矿化速率,计算土壤碳累积矿化量,探讨两种等浓度等量DOM添加对土壤碳矿化的影响,并分析DOM化学性质在土壤碳矿化过程中的重要性。结果表明:米槠凋落叶浸提得到的DOC(Dissolved organic carbon)和DON(Dissolved organic nitrogen)浓度均显著高于杉木凋落叶的(P0.05),而杉木凋落叶浸提得到的DOM的UV吸收值(SUVA_(254))和HIX(Humification index)均显著低于米槠凋落叶的(P0.01)。添加等浓度等量杉木和米槠凋落叶DOM到土壤中均显著增加了土壤碳矿化速率,在第1天内分别比对照高198%和168%,3d后下降到61.8%和44.1%,14d后基本处于平稳状态,表明外源有机物添加对土壤碳矿化的前期影响较大。培养过程中,添加杉木和米槠凋落叶DOM的土壤碳矿化累积量均能采用双因素指数模型进行拟合(r~2=0.99),但添加两者凋落叶DOM后土壤碳矿化累积量没有显著差异。     

A comparison of Fe bioavailability and binding of a catecholate siderophore with virus-mediated lysates from the marine bacterium Vibrio alginolyticus PWH3a

We have examined the bioavailability of Fe complexed to a siderophore produced by the heterotrophic marine bacterium Vibrio alginolyticus isolate PWH3a and Fe from ligand-complexes present in virus-mediated lysates (using phage PWH3a-P1) of this same bacterium. Fe-binding functional groups, stability constants and the bioavailability of Fe associated with these two separate ligand pools were determined and contrasted to previous work. Under low-Fe growth conditions, axenic cultures of V. alginolyticus PWH3a were shown to produce catecholate siderophores, while neither catecholate nor hydroxamate-type Fe-binding moieties were detected in virus-generated cell lysates. Analysis of the overall binding strength using electrochemical techniques revealed that the siderophore-containing organic extract and the organics in the virus-mediated lysates had Fe-binding constants comparable to the weaker L₂-type ligands found throughout the water column in seawater. A further purification of the siderophore-containing extract revealed a ligand with a stability constant of logK′_FeL,Fe3+ = 22.3, typical for siderophores and L₁-type of ligands found in marine surface waters. In assimilation studies, the Fe in the lysate was found to be more bioavailable to our model heterotrophic bacterium, autotrophic cyanobacterium and eukaryotic diatom cultures than the catecholate siderophore produced by the Vibrio sp. This work demonstrates that the Fe-containing components of virus-mediated cell lysates are different than siderophores secreted by these same cells, and as such continues to build the argument supporting the importance of virus-mediated Fe regeneration in marine surface waters.     

Spatiotemporal dynamics of the total and active Vibrio spp. populations throughout the Changjiang estuary in China

Vibrio is ubiquitously distributed in marine environments and is the most extensively characterized group within Gammaproteobacteria. Studies have investigated Vibrio spp. worldwide, but mostly focused on pathogenic vibrios and based on cultivation methods. Here, using a combination of molecular and culturing methods, we investigated the dynamics of the total and active Vibrio spp. throughout the Changjiang estuary in China. The total Vibrio abundance was higher in summer (~6.59 × 10³ copies ml⁻¹) than in winter (~1.85 × 10³ copies ml⁻¹) and increased from freshwater to saltwater (e.g. 8.04 × 10¹ to 9.39 × 10³ copies ml⁻¹ in summer). The ratio of active to total Vibrio (Va/Vt) revealed a high activity of vibrios, with remarkable differences between freshwater and saltwater (p < 0.05). Based on the community compositions of the culturable, total and active Vibrio, Vibrio atlanticus and Vibrio owensii were the dominant and active species in winter and summer, respectively. The distribution of Vibrio was governed by the effects of diverse environmental factors, such as temperature, salinity, pH, dissolved oxygen and SiO₃²⁻. Our study clearly demonstrates the spatiotemporal dynamics of total and active Vibrio spp. and lays a foundation for fully understanding the ecological roles of marine Vibrio.     

Bioactive chemical constituents produced by endophytes and effects on rice plant growth

We investigated the bioactive potential of fungal endophytes isolated from the roots of Glycine max (L.) Merr. and Cucumis sativus. Initial screening results showed that endophytes, (Chrysosporium pseudomerdarium, Aspergillus fumigates and Paecilomyces sp., Penicillium sp., Phoma glomerata, and Paecilomyces formosus) were promoting the growth attributes (shoot length, chlorophyll contents, and biomass) of mutant and wild-type rice. To know whether, these endophytes were producing bioactive chemical constituents; the endophytes were grown in potato dextrose, czapek broth, and ICI mediums that resulted in varying mycelia biomass. The advance chromatographic analysis of endophytic fungal culture filtrate showed gibberellins (GA) production namely GA₁ (0.05–10.55 ngml^?1), GA₃ (0.48–9.0 ngml^?1), GA₄ (0.2–8.0 ngml^?1), GA₇ (1.4–6.5 ngml^?1), and GA₉ (0.03–1.05 ngml^?1) while among endophytes, P. glomerata and P. formosus were highly potent in GAs production. Additionally, the endophyte's culture also contained indole-3-acetic acid (0.23–71.51 µgml^?1). Furthermore, oxalic (0.009–0.3 mgl^?1), quinic (0.019–0.22 mgl^?1), malic (1.94–17.2 mgl^?1), and citric (0.012–0.95 mgl^?1) acids were also present in the endophytic cultures. The biochemical potential of endophytes greatly varied depending on nutrient source and pH, however, czapek broth rich in carbon revealed higher potential for bioactive chemical constituent's production. In conclusion, the current findings suggest that endophyte can play a vital role in essential crop plant growth by synthesizing a wide array of bioactive metabolites. Furthermore, an increased production of chemical constituents can be achieved by changing the in vitro growth conditions of endophytes     

Effective biotic elicitation of <Emphasis Type="Italic">Ruta graveolens</Emphasis> L. shoot cultures by lysates from <Emphasis Type="Italic">Pectobacterium atrosepticum</Emphasis> and <Emphasis Type="Italic">Bacillus</Emphasis> sp.

Growth of Ruta graveolens shoots was induced when Bacillus sp. cell lysates were added to the culture medium. Elicitation of coumarin by this lysate was also very effective; the concentrations of isopimpinelin, xanthotoxin and bergapten increased to 610, 2120 and 1460 μg g⁻¹ dry wt, respectively. It also had a significant effect on the production of psoralen and rutamarin (680 and 380 μg g⁻¹ dry wt) and induced the biosynthesis of chalepin, which was not detected in the control sample, up to 47 μg g⁻¹ dry wt With lysates of the Pectobacterium atrosepticum, their effect on growth was not so significant and had no effect on the induction of coumarin accumulation. But elicitation with this lysate was much more effective for inducing the production of furoquinolone alkaloids; the concentrations of γ-fagarine, skimmianine, dictamnine and kokusaginine rose to 99, 680, 172 and 480 μg g⁻¹ dry wt, respectively.