Total Bacterial Numbers Research Articles

Novel soil fumigation method for suppressing cucumber Fusarium wilt disease associated with soil microflora alterations

Fusarium wilt in cucumber results from continuous cropping and is a serious soil-borne fungal disease that threatens cucumber production around the world. The application of a novel fumigation agent based on ammonium bicarbonate to the soil as a strategy for controlling Fusarium wilt and its effects on soil microflora was investigated in a field with serious disease incidence in this study. Overall, the results showed that fumigation effectively controlled cucumber Fusarium wilt disease and significantly increased the total and mean cucumber fruit weight. Real-Time PCR results showed that the total bacterial and fungal numbers in the treatment (LAB) significantly decreased after fumigation and that significantly fewer fungi were observed after harvest (LABOF). The next-generation sequencing of the 16S rRNA and internal transcribed spacer (ITS) genes using MiSeq platform showed that the soil bacterial and fungal community structures in the fumigation treatment were significantly different from the control without fumigation regardless after fumigation or harvest. Compared to the control, higher abundances of Gemmatimonadetes, Verrucomicrobia and Zygomycota, and lower abundance of Ascomycota were observed in the fumigated soils after fumigation and harvest. Furthermore, the abundances of Mortierella and Gp1 were significantly higher. Most importantly, the abundance of Fusarium, which includes the pathogen potentially responsible for cucumber Fusarium wilt disease, was significantly lower in the fumigated soils after harvest. Redundancy analysis showed that the fumigated soils were dominated by Ohtaekwangia, Gp6, and Gp4, which were related to the soil total nitrogen (TN), ammonium nitrogen (NH4–N) and nitrate nitrogen (NO3–N) contents. In addition, Penicillium and Pseudaleuria fungi were dominant in the treatment and control, and the control was dominated by Fusarium. In conclusion, the observed disease suppression due to the novel ecological soil fumigation strategy may be attributed to general suppression resulting from altered soil properties, such as higher soil NH4–N, NO3–N and TON contents, and the alteration of the disturbed soil microflora in a cucumber monoculture system.

Influence of green algae Chlorella vulgaris on initial growth of different agricultural crops

The aim of this research was to evaluate the effect of green algae Chlorella vulgaris on the initial growth of wheat, maize, bean and lettuce and the microbiological activity of rhizospheric soil. The experiment was conducted in controlled conditions. The inocula were applied as foliar fertilizer by spraying. Plant material was taken 30 days after plant emergance. Chlorella vulgaris affected positively the length (28.5% increase) and fresh mass (17.9% increase) of maize root, stem length of wheat (24.2% increase) and stem mass of lettuce (56.34% increase). Application of Chlorella vulgaris led to the increase of the total number of bacteria and the number of aminoheterotrophs in the maize rhizosphere, total bacterial number in the wheat rhizosphere, and the number of fungi in the rhizosphere of bean. The number of other investigated groups of microorganisms did not change significantly. The activity of dehydrogenase enzyme was not affected by inoculation with green algae.

Water heater temperature set point and water use patterns influence Legionella pneumophila and associated microorganisms at the tap.

BackgroundLowering water heater temperature set points and using less drinking water are common approaches to conserving water and energy; yet, there are discrepancies in past literature regarding the effects of water heater temperature and water use patterns on the occurrence of opportunistic pathogens, in particular Legionella pneumophila. Our objective was to conduct a controlled, replicated pilot-scale investigation to address this knowledge gap using continuously recirculating water heaters to examine five water heater set points (39–58 °C) under three water use conditions. We hypothesized that L. pneumophila levels at the tap depend on the collective influence of water heater temperature, flow frequency, and the resident plumbing ecology.ResultsWe confirmed temperature setting to be a critical factor in suppressing L. pneumophila growth both in continuously recirculating hot water lines and at distal taps. For example, at 51 °C, planktonic L. pneumophila in recirculating lines was reduced by a factor of 28.7 compared to 39 °C and was prevented from re-colonizing biofilm. However, L. pneumophila still persisted up to 58 °C, with evidence that it was growing under the conditions of this study. Further, exposure to 51 °C water in a low-use tap appeared to optimally select for L. pneumophila (e.g., 125 times greater numbers than in high-use taps). We subsequently explored relationships among L. pneumophila and other ecologically relevant microbes, noting that elevated temperature did not have a general disinfecting effect in terms of total bacterial numbers. We documented the relationship between L. pneumophila and Legionella spp., and noted several instances of correlations with Vermamoeba vermiformis, and generally found that there is a dynamic relationship with this amoeba host over the range of temperatures and water use frequencies examined.ConclusionsOur study provides a new window of understanding into the microbial ecology of potable hot water systems and helps to resolve past discrepancies in the literature regarding the influence of water temperature and stagnation on L. pneumophila, which is the cause of a growing number of outbreaks. This work is especially timely, given society’s movement towards “green” buildings and the need to reconcile innovations in building design with public health.Electronic supplementary materialThe online version of this article (doi:10.1186/s40168-015-0134-1) contains supplementary material, which is available to authorized users.

Taxonomic characterization and the bio-potential of bacteria isolated from glacier ice cores in the High Arctic.

Glacier ice and firn cores have ecological and biotechnological importance. The present study is aimed at characterizing bacteria in crustal ice cores from Svalbard, the Arctic. Counts of viable isolates ranged from 10 to 7000 CFU/ml (mean 803 CFU/ml) while the total bacterial numbers ranged from 7.20 × 10(4) to 2.59 × 10(7) cells ml(-1) (mean 3.12 × 10(6) cells ml(-1) ). Based on 16S rDNA sequence data, the identified species belonged to seven species, namely Bacillus barbaricus, Pseudomonas orientalis, Pseudomonas oryzihabitans, Pseudomonas fluorescens, Pseudomonas syncyanea, Sphingomonas dokdonensis, and Sphingomonas phyllosphaerae, with a sequence similarity ranging between 93.5 and 99.9% with taxa present in the database. The isolates exhibited unique phenotypic properties, and three isolates (MLB-2, MLB-5, and MLB-9) are novel species, yet to be described. To the best of our knowledge, this is the first report on characterization of cultured bacterial communities from Svalbard ice cores. We conclude that high lipase, protease, cellulase, amylase, and urease activities expressed by most of the isolates provide a clue to the potential industrial applications of these organisms. These microbes, producing cold-adapted enzymes may provide an opportunity for biotechnological research.

Selective elimination of bacterial faecal indicators in the Schmutzdecke of slow sand filtration columns.

Slow sand filtration (SSF) is an effective low-tech water treatment method for pathogen and particle removal. Yet despite its application for centuries, it has been uncertain to which extent pathogenic microbes are removed by mechanical filtration or due to ecological interactions such as grazing and competition for nutrients. In this study, we quantified the removal of bacterial faecal indicators, Escherichia coli and Enterococcus faecalis, from secondary effluent of a wastewater treatment plant and analysed the microbial community composition in compartments of laboratory model SSF columns. The columns were packed with different sand grain sizes and eliminated 1.6-2.3 log units of faecal indicators, which translated into effluents of bathing water quality according to the EU directive (<500 colony forming units of E. coli per 100ml) for columns with small grain size. Most of that removal occurred in the upper filter area, the Schmutzdecke. Within that same zone, total bacterial numbers increased however, thus suggesting a specific elimination of the faecal indicators. The analysis of the microbial communities also revealed that some taxa were removed more from the wastewater than others. These results accentuate the contribution of biological mechanisms to water purification in SSF.

Effect of a multispecies lactobacillus formulation as a feeding supplement on the performance and immune function of piglets

Lactobacilli are essential members of the swine intestinal microbiota, with proposed health promoting effects. There is a reduction in the abundance of intestinal lactobacilli around weaning; this has been considered to predispose piglets to gut disturbances, e.g. diarrhea. Therefore, dietary supplementation with lactobacilli may help in maintaining better host health around weaning. In this study, we assessed the efficacy of a bacterial supplement containing six strains of the genus Lactobacillus in a feeding trial conducted in recently weaned pigs. Twenty piglets were divided into two groups (n=10) based on litter origin. Piglets in the supplementation group were fed the lactobacilli mixture (total cell count 1×1010) daily for three weeks, while those in the control group were provided with a probiotic-free placebo. The aim of this study was to evaluate the intestinal survivability of the feeding strains, as well as the effects of the supplementation on the performance of the piglets. Furthermore, the expression of selected cytokines was analyzed in the gut mucosa. The main effect of the lactobacilli supplementation observed was immunomodulation in the piglet intestine, especially in the large intestine. Upregulated expressions of IL-4 and IFN-α were detected in the cecum, with downregulated expressions of IL-8 and TNF in the colon of the supplementation group. In addition, supplementation downregulated the expression of TGF-β1 in the jejunum, ileum and colon. An increased total bacterial number was detected in the jejunum of the supplementation group, but no change in the intestinal digesta pH or in the numbers of lactobacilli was induced by the supplementation. In addition, the strains which had been supplied could not be isolated from feces, indicating that they had been unable to colonize the piglet intestine in significant numbers. The lactobacilli supplementation had no effect on the weight gain or the intestinal mucosal morphology of the piglets. While the lactobacilli supplement used in this study failed to achieve a growth-enhancing effect, and the supplemented strains appeared to have a limited ability to compete with the indigenous intestinal microbiota of piglets, the supplement evoked immunomodulatory properties in the piglet intestine.

Seagrass vegetation and meiofauna enhance the bacterial abundance in the Baltic Sea sediments (Puck Bay).

This study presents the first report on bacterial communities in the sediments of eelgrass (Zostera marina) meadows in the shallow southern Baltic Sea (Puck Bay). Total bacterial cell numbers (TBNs) and bacteria biomass (BBM) assessed with the use of epifluorescence microscope and Norland’s formula were compared between bare and vegetated sediments at two localities and in two sampling summer months. Significantly higher TBNs and BBM (PERMANOVA tests, P < 0.05) were recorded at bottom covered by the seagrass meadows in both localities and in both sampling months. The relationships between bacteria characteristics and environmental factors (grain size, organic matter, photopigments in sediments), meiofauna and macrofauna densities, as well as macrophyte vegetation characteristics (shoot density, phytobenthos biomass) were tested using PERMANOVA distance-based linear model (DISTLM) procedures and showed that the main factors explaining bacteria characteristics are bottom type (vegetated vs. unvegetated) and meiofauna density. These two factors explained together 48.3 % of variability in TBN and 40.5 % in BBM, and their impacts did not overlap (as indicated by DISTLM sequential tests) demonstrating the different natures of these relationships. The effects of seagrass were most probably related to the increase of organic matter and providing habitat while higher numbers of meiofauna organisms may have stimulated the bacterial growth by increased grazing.

Postnatal bacterial succession and functional establishment of hindgut in supplemental feeding and grazing goats.

The objectives of this study were 1) to investigate the age-related changes in functional achievement (establishment of fermentation capacity and enzyme activities) and bacterial succession (selected functional bacterial species) in the cecum and colon and 2) to assess the effect of feeding system (supplemental vs. grazing, Sup vs. G) on hindgut development in small ruminants. A total of 44 Liuyang black goat kids were randomly slaughtered at 0, 7, and 14 d of age (nonrumination period), 28 and 42 d of age (transition period), and 56 and 70 d of age (rumination period). Intestinal contents were sampled to determine VFA, activities of amylase, carboxymethylcellulase (CMCase), and xylanase, as well as abundances of total bacteria and selected functional bacterial species (genus Prevotella, cellulolytic and amylolytic bacteria) with quantitative PCR targeting the 16S rRNA subunit genes. Total VFA concentration (P < 0.01) and enzyme activities (P < 0.05) in hindgut contents were greater and total bacterial 16S rRNA gene copy numbers (P = 0.003) in the cecum were lower for Sup vs. G. Furthermore, irrespective of feeding system, hindgut total VFA concentrations and total bacterial 16S rRNA gene copy numbers increased with age (P < 0.01), with the greatest increase rate observed from 14 to 28 d. Amylase fluctuated with age, whereas CMCase and xylanase activities in Sup kids increased (P < 0.05) as age increased. The proportions of 16S rRNA copy numbers associated with the genus Prevotella and P. ruminicola increased (P < 0.05) with age, but those of cellulolytic bacteria and Ruminobacter amylophilus were detected only after 28 d of birth. The bacterial succession, fermentation capacity, and starch-degrading capacity in the hindgut of both groups were achieved at 1 mo, whereas fiber-degrading capacity in Sup kids was established at 2 mo of age; and supplemental feeding surpassed the grazing system in shaping hindgut development.

Toxicity of zero-valent iron nanoparticles to a trichloroethylene-degrading groundwater microbial community

The microbiological impact of zero-valent iron used in the remediation of groundwater was investigated by exposing a trichloroethylene-degrading anaerobic microbial community to two types of iron nanoparticles. Changes in total bacterial and archaeal population numbers were analyzed using qPCR and were compared to results from a blank and negative control to assess for microbial toxicity. Additionally, the results were compared to those of samples exposed to silver nanoparticles and iron filings in an attempt to discern the source of toxicity. Statistical analysis revealed that the three different iron treatments were equally toxic to the total bacteria and archaea populations, as compared with the controls. Conversely, the silver nanoparticles had a limited statistical impact when compared to the controls and increased the microbial populations in some instances. Therefore, the findings suggest that zero-valent iron toxicity does not result from a unique nanoparticle-based effect.

UV-C treatments enhance antioxidant activity, retain quality and microbial safety of fresh-cut paprika in MA storage

Fresh-cut paprika was treated with 245 nm UV-C irradiations of 7, 15, and 28 kJ·m-2, packaged using a laser ablation breathable film with permeability of 20,000 mL O2·m-2·day-1·atm-1, and was stored in general distribution temperature at 8°C. The paprikas were evaluated antioxidant activity and internal quality, reducing microbial populations, modifying composition of CO2, O2 and ethylene content in packages. Fresh-cut paprika irradiated with 15 kJ·m-2 UV-C has shown the lowest fresh weight loss and highest overall quality during MA storage. The gas composition (CO2 and O2 concentrations) of UV-C 15 kJ·m-2 treatment showed the closest conditions to CA conditions of paprika. All UV-C treatments presented higher ethylene concentration in package as compared to those of the control as well as NaOCl treatment, because the ethylene content was elevated in response to abiotic stress, possibly by the treatment of UV-C in paprika. After 7 days of storage at 8°C, the antioxidant activity (DPPH activity), total phenolic compound and vitamin C contents of fresh-cut paprika were maintained highest by UV-C 15 kJ·m-2 treatments, followed by 7 kJ·m-2 and 28 kJ·m-2. The microbial population was reduced by UV-C treatment on the 7 days of MA storage, with the fungal incidence rate lowest in 15 kJ·m-2 and 28 kJ·m-2 UV-C treatment and total bacterial numbers showed the lowest in UV-C 15 kJ·m-2 treatment representing lower than 6.0 log CFU·g-1 which was the reference limit for microbial contamination. These results suggest that the application of UV-C 15 kJ·m-2 on fresh-cut paprika represents the most favorable results of gas composition in package, antioxidant capacity (e.g., vitamin C contents) and sterilization of fungi and bacteria during MA storage, and extending the shelf life.

Long term Impact of a Disinfectant with Residual Activity on Suppression of Bacteria on Fomites in Hospital Waiting Rooms

Long term Impact of a Disinfectant with Residual Activity on Suppression of Bacteria on Fomites in Hospital Waiting Rooms

Intestinal microbiota of striped catfish, Pangasianodon hypophthalmus (Sauvage, 1878) fed on dietary nucleotide

The aim of this study was to assess the effects of nucleotide on intestinal microbiota of striped catfish, Pangasianodon hypophthalmus . Different levels of the NT (0, 0.25. 0.5, 0.75 and 1 % weight per weight, WW -1 ) were added to basal diet and then randomly allocated to triplicate groups of fish with average initial weight (1.52±0.11 g) for 10 weeks. At the end of the experiment, at least 10 individual fish from each treatment were used to study quantitative and qualitative analyses of bacterial flora of intestine. The bacterial flora was identified to species level where possible. Total viable bacterial counts in the intestine of the catfish ranged from 4.33±0.49×10 4 , 5.98±0.82×10 4 , 6.44±1.09×10 4 , 5.54±0.64×10 4 and 2.65±0.46×10 4 colony forming units (cfu/g) for groups treated with 0-1% NT respectively without any significant difference among groups (P>0.05). Gram negative rod shaped bacteria were dominant in all groups. Altogether 16 bacterial species of 12 genera were identified in total populations. Most of the bacterial species were common among all groups. Proteus mirabilis , Serratia liquefaciens , Bacillus cereus only were observed in NT treated fish while Alkaligenes faecalis only existed in the control group. Corynebacterium urealyticum and Staphylococcus aureus were identified in some fish belong to control-0.25 NT and control 1-NT groups respectively. The results of this study demonstrate that although the total bacterial count number did not affected by dietary NT but some qualitative changes were clearly observed.

Pesticide Side Effects in an Agricultural Soil Ecosystem as Measured by amoA Expression Quantification and Bacterial Diversity Changes

Background and MethodsAssessing the effects of pesticide hazards on microbiological processes in the soil is currently based on analyses that provide limited insight into the ongoing processes. This study proposes a more comprehensive approach. The side effects of pesticides may appear as changes in the expression of specific microbial genes or as changes in diversity. To assess the impact of pesticides on gene expression, we focused on the amoA gene, which is involved in ammonia oxidation. We prepared soil microcosms and exposed them to dazomet, mancozeb or no pesticide. We hypothesized that the amount of amoA transcript decreases upon pesticide application, and to test this hypothesis, we used reverse-transcription qPCR. We also hypothesized that bacterial diversity is affected by pesticides. This hypothesis was investigated via 454 sequencing and diversity analysis of the 16S ribosomal RNA and RNA genes, representing the active and total soil bacterial communities, respectively.Results and ConclusionTreatment with dazomet reduced both the bacterial and archaeal amoA transcript numbers by more than two log units and produced long-term effects for more than 28 days. Mancozeb also inhibited the numbers of amoA transcripts, but only transiently. The bacterial and archaeal amoA transcripts were both sensitive bioindicators of pesticide side effects. Additionally, the numbers of bacterial amoA transcripts correlated with nitrate production in N-amended microcosms. Dazomet reduced the total bacterial numbers by one log unit, but the population size was restored after twelve days. The diversity of the active soil bacteria also seemed to be re-established after twelve days. However, the total bacterial diversity as reflected in the 16S ribosomal RNA gene sequences was largely dominated by Firmicutes and Proteobacteria at day twelve, likely reflecting a halt in the growth of early opportunists and the re-establishment of a more diverse population. We observed no effects of mancozeb on diversity.

Changes in composition of caecal microbiota associated with increased colon inflammation in interleukin-10 gene-deficient mice inoculated with Enterococcus species.

Human inflammatory bowel disease (IBD) is a chronic intestinal disease where the resident microbiota contributes to disease development, yet the specific mechanisms remain unclear. Interleukin-10 gene-deficient (Il10-/-) mice develop inflammation similar to IBD, due in part to an inappropriate response to commensal bacteria. We have previously reported changes in intestinal morphology and colonic gene expression in Il10-/- mice in response to oral bacterial inoculation. In this study, we aimed to identify specific changes in the caecal microbiota associated with colonic inflammation in these mice. The microbiota was evaluated using pyrotag sequencing, denaturing gradient gel electrophoresis (DGGE) and quantitative real-time PCR. Microbiota profiles were influenced by genotype of the mice and by bacterial inoculation, and a strong correlation was observed between the microbiota and colonic inflammation scores. Although un-inoculated Il10-/- and C57 mice had similar microbiota communities, bacterial inoculation resulted in different changes to the microbiota in Il10-/- and C57 mice. Inoculated Il10-/- mice had significantly less total bacteria than un-inoculated Il10-/- mice, with a strong negative correlation between total bacterial numbers, relative abundance of Escherichia/Shigella, microbiota diversity, and colonic inflammation score. Our results show a putative causative role for the microbiota in the development of IBD, with potentially key roles for Akkermansia, or for Bacteroides, Helicobacter, Parabacteroides, and Alistipes, depending on the composition of the bacterial inoculum. These data support the use of bacterially-inoculated Il10-/- mice as an appropriate model to investigate human IBD.

The Impact of Mineral Nitrogen Fertilization on the Occurrence of Native Diazotrophic Bacteria in Kohlrabi (Brassica oleracea) Shoots and Roots

Biological Nitrogen Fixation (BNF) is a process of great importance in crop production systems, as it provides additional natural sources of mineral nitrogen. BNF is catalyzed by diazotrophs that are identified by the nif operon presence comprising the nifH gene that encodes for enzyme nitrogenase synthesis. Thoroughly understanding of factors that influence diazotrophic abundance is crucial for their utilization to enhance sustainability and prevent land degradation in modern agriculture. In this study the impacts of nitrogen fertilization on diazotrophic abundance in Brassica oleracea roots and leaves was investigated in greenhouse experiments by real-time qPCR. One way ANOVA was used to compare means and bivariate Pearson correlation tested for relationships between variables. Increased nitrogen fertilization significantly increased the nitrogen content in leaves but not in roots. No significant changes in nifH gene copy numbers nor in proportion of nifH gene copy numbers were detectable. This indicates no effect of mineral N fertilization on the abundance of total native diazotrophic bacterial numbers in Brassica oleracea plants.

Microbial Diversity of Ammonia Oxidizing and Other Bacteria of Activated Sludge

Microbial diversity and large quantity of ammonia-oxidizing bacteria (AOB) in activated sludge were compared using PCR-DGGE and real-time PCR assays. Activated sludge samples were collected from different types of wastewater treatment plants (WWTPs). The composition of total bacteria determined by PCR-DGGE was highly diverse between the samples, whereas the community of AOB was similar across all the investigated activated sludge. Total bacterial numbers and AOB numbers in the aerated mixed liquor were in the range of 1.2×10<SUP>9</SUP> to 2.8×10<SUP>12</SUP> and 1.9×10<SUP>7</SUP> to 2.7×10<SUP>10</SUP> copies/l, respectively. Activated sludge from livestock, textile, and sewage treating WWTPs contained relatively high amoA gene copies (more than 10<SUP>5</SUP> copies/l), whereas activated sludge from food and paper WWTPs revealed a low number of the amoA gene (less than 10<SUP>3</SUP> copies/l). The value of the amoA gene copy effectively showed the difference in composition of bacteria in different activated sludge samples and this was better than the measurement with the AOB 16S rRNA or total 16S rRNA gene. These results suggest that the quantification of the amoA gene can help monitor AOB and ammonia oxidation in WWTPs.

Mycobacterium tuberculosis Strains Lacking Surface Lipid Phthiocerol Dimycocerosate Are Susceptible to Killing by an Early Innate Host Response

The innate immune response plays an important but unknown role in host defense against Mycobacterium tuberculosis. To define the function of innate immunity during tuberculosis, we evaluated M. tuberculosis replication dynamics during murine infection. Our data show that the early pulmonary innate immune response limits M. tuberculosis replication in a MyD88-dependent manner. Strikingly, we found that little M. tuberculosis cell death occurs during the first 2 weeks of infection. In contrast, M. tuberculosis cells deficient in the surface lipid phthiocerol dimycocerosate (PDIM) exhibited significant death rates, and consequently, total bacterial numbers were reduced. Host restriction of PDIM-deficient M. tuberculosis was not alleviated by the absence of interferon gamma (IFN-γ), inducible nitric oxide synthase (iNOS), or the phagocyte oxidase subunit p47. Taken together, these data indicate that PDIM protects M. tuberculosis from an early innate host response that is independent of IFN-γ, reactive nitrogen intermediates, and reactive oxygen species. By employing a pathogen replication tracking tool to evaluate M. tuberculosis replication and death during infection, we identify both host and pathogen factors affecting the outcome of infection.

The effect of vermifiltration height and wet:dry time ratio on nutrient removal performance and biological features, and their influence on nutrient removal efficiencies

We investigated the effects of vermifiltration (VF) height and the wet:dry time (WD) ratio on nutrient removal from synthetic domestic wastewater, earthworm population characteristics, and microbial numbers in the substrate. We also evaluated the key factors influencing nutrient removal. Results showed that variation in VF height had a significant effect on chemical oxygen demand (COD) and total phosphate (TP) removal rates, earthworm population, and actinomycetes numbers, but had no effect on ammonia nitrogen (NH3-N) and total nitrogen (TN) removal rates, and bacterial and fungi numbers. All parameters, except TP removal and fungi numbers, were significantly affected by variation in the WD ratio. Furthermore, when combined, the VF height and the WD ratio significantly influenced the earthworm reproduction rate and actinomycetes numbers. In particular, good nutrient removal efficiencies, vigorous earthworm activity and high microbial numbers were observed when the WD ratio was 1/3 and the VF height was 60cm. Results suggest that earthworm growth and reproduction rates, fungi, and actinomycetes numbers are good indicators of the COD and TP removal efficiencies by VF. These factors, along with the bacterial numbers, are good indicators of NH3-N removal efficiency; however, only the earthworm growth rate and actinomycetes numbers are useful indicators for the TN removal efficiency from wastewater by VF.

Evaluation of relationship between Chilean octopus (Octopus mimusGould, 1852) egg health condition and the egg bacterial community

The objective of this study was to evaluate how bacterial community associated with Chilean octopus (Octopus mimus) egg was related to egg health condition using a culture dependent method and PCR-DGGE fingerprinting technique. Total heterotrophic bacterial number of fresh egg was much lower than infected egg. However, biodiversity of culturable bacterial community associated with the fresh egg exhibited a higher diversity than the infected egg. Result of a culture dependent method showed that Roseobacter clade was predominant in the fresh egg, while predominant species in the infected egg was γ-proteobacteria. DGGE fingerprinting technique showed that fresh egg associated unculturable bacterial community was constituted of Roseobacter clade and Bacteroidetes, whereas Bacteroidetes was predominant bacteria in the infected egg. These results suggest that there might be some sort of relationship between octopus eggs associated bacterial community and egg health condition. Moreover, Roseobacter clade and Bacteroidetes might be potential symbiotic bacteria associated with the octopus egg, and some γ-proteobacteria might be involved in octopus egg disease. In particular, Roseobacter clade may play an important role in octopus egg health and it raises the possibility that this clade can be utilized as potential probiotics for octopus aquaculture.

A microcosm approach to evaluate the degradation of tributyltin (TBT) by Aeromonas molluscorum Av27 in estuarine sediments

Tributyltin (TBT) is a biocide extremely toxic to a wide range of organisms, which has been used for decades in antifouling paints. Despite its global ban in 2008, TBT is still a problem of great concern due to the high levels trapped in sediments. Aeromonas molluscorum Av27 is a TBT degrading bacterium that was isolated from an estuarine system. We investigated the ability and the role of this bacterium on TBT degradation in this estuarine system, using a microcosm approach in order to mimic environmental conditions. The experiment was established and followed for 150 days. Simultaneously, changes in the indigenous bacterial community structure were also investigated. The results revealed a maximum TBT degradation rate of 28% accompanied by the detection of the degradation products over time. Additionally, it was observed that TBT degradation was significantly enhanced by the presence of Av27. In addition a significantly higher TBT degradation occurred when the concentration of Av27 was higher. TBT degradation affected the bacterial community composition as revealed by the changes in the prevalence of Proteobacteria subdivisions, namely the increase of Deltaproteobacteria and the onset of Epsilonproteobacteria. However, the addition of Av27 strain did not affect the dominant phylotypes. Total bacterial number, bacterial biomass productivity, 16S rRNA gene and denaturing gradient gel electrophoresis (DGGE) analyses also indicated alterations on the bacterial community structure over time, with bacteria non-tolerant to pollutants increasing their representativeness, as, for instance, the increase of the number of Alphaproteobacteria clones from 6% in the beginning to 12% at the end of the experiment. The work herein presented confirms the potential of Av27 strain to be used in the decontamination of TBT-polluted environments.