Growth Of Mixed Cultures Research Articles

Growth assessment of mixed cultures of probiotics and common pathogens

ObjectivesIn this work, an isothermal microcalorimeter was applied to investigate the antipathogenic activity of three probiotics (Lactobacillus acidophilus, Bifidobacterium lactis and Bifidobacterium bifidum) against Pseudomonas aeruginosa, Staphylococcus aureus and Escherichia coli using the probiotics in mixed culture with the pathogenic microorganisms. MethodsA microcalorimeter was used to monitor the growth of the microorganisms as pure cultures and as co-cultures at 37 °C. Relative growths of the probiotics and pathogenic species were determined after microcalorimetric measurements by serial dilution and plate incubation. Relative growth of mixed cultures of E. coli with L. acidophilus or B. lactis was also determined by traditional plate growth assay for 5.5 h. ResultsThe results showed growth profiles of the microorganisms that were characteristic and showed different lag and peak times for the species. The pathogenic species grew faster than the probiotic species. In the co-cultures, the growth profile of both pathogenic species and probiotics could be identified with the microcalorimeter. Although the pathogenic species grew faster, at the end of the assay, the results showed that the pathogenic species were inhibited in growth by the probiotics as no viable growth of the pathogenic species was detected whereas 107–108 CFU/mL of the probiotics were enumerated after the microcalorimetric assay. Using the traditional plate assay, the data confirmed co-growth of the probiotics and E. coli although cell numbers of E. coli were higher than the probiotics during 5.5 h of co-culture incubation when both were inoculated at 106 CFU/mL. ConclusionThe results demonstrate the antipathogenic effects of probiotics and highlights the potential of microcalorimetry in live mixed culture assays and its limitation.

The Role of Mycotoxins in Interactions between Fusarium graminearum and F. verticillioides Growing in Saprophytic Cultures and Co-Infecting Maize Plants.

Fusarium graminearum (FG) and Fusarium verticillioides (FV) co-occur in infected plants and plant residues. In maize ears, the growth of FV is stimulated while FG is suppressed. To elucidate the role of mycotoxins in these effects, we used FG mutants with disrupted synthesis of nivalenol (NIV) and deoxynivalenol (DON) and a FV mutant with disrupted synthesis of fumonisins to monitor fungal growth in mixed cultures in vitro and in co-infected plants by real-time PCR. In autoclaved grains as well as in maize ears, the growth of FV was stimulated by FG regardless of the production of DON or NIV by the latter, whereas the growth of FG was suppressed. In autoclaved grains, fumonisin-producing FV suppressed FG more strongly than a fumonisin-nonproducing strain, indicating that fumonisins act as interference competition agents. In co-infected maize ears, FG suppression was independent of fumonisin production by FV, likely due to heterogeneous infection and a lower level of fumonisins in planta. We conclude that (i) fumonisins are agents of interference competition of FV, and (ii) trichothecenes play no role in the interaction between FG and FV. We hypothesize the following: (i) In vitro, FG stimulates the FV growth by secreting hydrolases that mobilize nutrients. In planta, suppression of plant defense by FG may additionally play a role. (ii) The biological function of fumonisin production in planta is to protect kernels shed on the ground by accumulating protective metabolites before competitors become established. Therefore, to decipher the biological function of mycotoxins, the entire life history of mycotoxin producers must be considered.

Two-Phase Partitioning Bioreactor for the Treatment of Crude Oil- Contaminated Aqueous Solution

A new application of a combined solvent extraction and two-phase biodegradation processes using two-liquid phase partitioning bioreactor (TLPPB) technique was proposed and developed to enhance the cleanup of high concentration of crude oil from aqueous phase using acclimated mixed culture in an anaerobic environment. Silicone oil was used as the organic extractive phase for being a water-immiscible, biocompatible and non-biodegradable. Acclimation, cell growth of mixed cultures, and biodegradation of crude oil in aqueous samples were experimentally studied at 30±2ºC. Anaerobic biodegradation of crude oil was examined at four different initial concentrations of crude oil including 500, 1000, 2000, and 5000 mg/L. Complete removal of crude oil was achieved biphasic bioreactor after 3 weeks compared to 73-82% in the monophasic bioreactor for the same time period.

Interaction of Cropping Pattern and Fertility Treatments on Yield and Sustainability of Mixed Cropping System under Moisture Regime

The farmers in most regions of Pakistan are heavily reliant on traditional farming approaches all year round and tend to cultivate exhaustive crops like wheat, cotton, maize, and sugarcane in most areas of the country. Consistently adopting this system leads to depleting the soil fertility status, which they overcome by instigating an uneconomical way of using excessive chemical fertilizers to maximize crop yields. These fertilizers are truly acidic and adversely affect soil health. Adopting sustainable farming approaches by the incorporation of legumes into the farming system with an integrated nutrient supply restores soil fertility and maintains the sustainability of the agro-ecosystem. A field experiment was performed to determine the significance of the integrated source of nutrient management on the growth and yield of sole and mixed cultures of sorghum and mungbean crops in areas with moisture regimes. The fertility treatments applied to the sole and intercrops of sorghum and mung-bean in a given sequence; i) Control, ii) Compost @ 10 t/ha, iii) FYM @ 20 t/ha, iv) NP @ 40 kg N + 30 kg P2O5 ha-1, v) ½ of recommended Compost @ 5 t/ha + ½ of recommended NP @ 20 kg N & 15 kg P2O5 ha-1, vi) ½ of recommended FYM @ 10 t/ha + ½ of recommended NP @ 20 kg N & 15 kg P2O5 ha-1. The sole crop of mungbean gave a maximum grain yield of 2229.1 kg/ha over an intercrop of 1779.7 kg/ha. Similarly, the highest grain yield of 2779.8 kg/ha of sorghum was obtained in sole culture over its intercrop of 2150.9 kg/ha. The interaction effect of cropping pattern and fertility treatments showed that sorghum and mungbean gave significant results for growth and yield parameters where a combined dose of organic & mineral fertilizers were provided in comparison to the plots where these fertilizers were applied in split doses.

Determining the best anti-microbial properties of dental cements used for pulp capping procedures using deep dentinal carious material.

The exposure of the healthy pulp in cases of deep dentinal caries (DDC) that contain carious microorganisms can be prevented by placing a layer of pulp capping agent on the affected dentin. The cements used for pulp-capping should also ensure good anti-microbial properties. The present study was carried out to detect the antimicrobial efficacy of the commonly used cements by culturing the samples directly from DDC. To determine the efficacy of dental cements in the growth inhibition of microorganisms involved in DDC using direct contact anaerobic culture test. 100 samples of DDC were collected in RTF. Ten microliters of the specimen containing RTF was incubated in thioglycolate broth consisting of 1 mm3 cement blocks of GIC, CaOH2, ZnOE and MTA anaerobically for 24 hours. This was further sub-cultured using selective media for streptococcus mutans, lactobacillus and bifidobacterium. Growth inhibition was measured by calculating the number of CFUs and statistically analysed using ANOVA and Tukey's post-hoc tests. Tests showed variation in the anti-microbial effects of the cements and was highly significant at P < 0.001. Bifidobacterium showed most number of CFUs. MTA was the most effective pulp capping agent exhibiting 87.13% reduction in microbial growth, followed closely by ZnOE (84.6%). A conservative approach to treat DDC is the need of the hour which calls for the use of pulp capping cements of good antimicrobial efficacy. The current study revealed bifidobacterium to be the most prevalent in DDC and the cement that would best inhibit the mixed culture growth was MTA followed closely by ZnOE.

Relative Rate of Maternal Deaths in Pakistani Population due to sepsis

Aim: To investigate the relative rate of maternal deaths in Pakistani population due to sepsis including the most common causative agent. Methods: The proposed study was a retrospective study model which was mainly conducted at a tertiary care hospital of Lodhran district-Punjab, Pakistan from 2019-2021 in association with the cases of maternal deaths due to sepsis reported and observed at the Gynecology &amp; Obstetrics department of different tertiary care hospitals. Total 1200 number of participants had been examined in this study and the convenient sampling technique was used. Whereas, it discusses the maternal mortalities due to different types of sepsis during, between, and after the delivery of a baby. with diagnosed 50% cases reported for the maternal deaths due to sepsis. Data was analyzed using SPSS VR 20.0 with level of significance being kept at P-value &lt;0.001. Results:As per the observation, out of 1200 samples, 640 samples were culture-positive, including mixed culture growth. Highest percent positivity was showed up by Streptococcus pyogenes 640(53.33%), followed by Chlamydia psittaci 80(6.66%), Mycobacterium tuberculosis 120(10%), Escherichia coli 80(6.66%), Neisseria meningitidis 40(3.33%), and Epstein-Bar virus 40(3.33%). Different approaches of delivery, gender, and respiratory infections, and the time of admission to the hospital along with the qSOFA (Quick Sequential Organ Failure Assessment) Criteria were significantly associated with sepsis. ConclusionGroup A Streptococcus (i.e.Streptococcus pyogenes strains) were the most active causative agents 640(53.33%) in inducing maternal sepsis leading to deaths. Therefore, proper preventive measures should be taken before, during and after the delivery (antepartum, post-partum) to reduce the dependent and independent risk factors and subsequently to decrease the burden of maternal deaths due to sepsis. Keywords: Maternal, Sepsis, death, culture, Streptococcus pyogenes, GAS.

Urine Flow Cytometry Parameter Cannot Safely Predict Contamination of Urine-A Cohort Study of a Swiss Emergency Department Using Machine Learning Techniques.

Background: Urine flow cytometry (UFC) analyses urine samples and determines parameter counts. We aimed to predict different types of urine culture growth, including mixed growth indicating urine culture contamination. Methods: A retrospective cohort study (07/2017–09/2020) was performed on pairs of urine samples and urine cultures obtained from adult emergency department patients. The dataset was split into a training (75%) and validation set (25%). Statistical analysis was performed using a machine learning approach with extreme gradient boosting to predict urine culture growth types (i.e., negative, positive, and mixed) using UFC parameters obtained by UF-4000, sex, and age. Results: In total, 3835 urine samples were included. Detection of squamous epithelial cells, bacteria, and leukocytes by UFC were associated with the different types of culture growth. We achieved a prediction accuracy of 80% in the three-class approach. Of the n = 126 mixed cultures in the validation set, 11.1% were correctly predicted; positive and negative cultures were correctly predicted in 74.0% and 96.3%. Conclusions: Significant bacterial growth can be safely ruled out using UFC parameters. However, positive urine culture growth (rule in) or even mixed culture growth (suggesting contamination) cannot be adequately predicted using UFC parameters alone. Squamous epithelial cells are associated with mixed culture growth.

The impact of light intensity and wavelength on the performance of algal-bacterial culture treating domestic wastewater

Light is the main energy source for microalgae, and the intensity and wavelength of light influence cell metabolism and biomass composition, which, in turn, affects wastewater treatment. The objective of this study is to examine how different light intensities and light wavelengths affect the growth of mixed algal-bacterial culture while treating sewage. Three different light intensities (100, 200, and 300 μmol/m2-s) of four different light wavelengths (blue, red, white, and yellow) were selected for this study. The dissolved organic carbon (DOC), dissolved nitrogen (DN), and dissolved phosphorus (DP) in influent and effluent samples were measured, along with chlorophyll content in the biomass. The highest chlorophyll concentration of 3.5 mg/L was observed at 100 μmol/m2-s intensity of red light. The concentration of chlorophyll decreased as light intensity increased, with exception of white light. The highest DOC removal of 84% was observed at 300 μmol/m2-s intensity of blue light whereas the highest DN (51%) and DP (80%) removal was observed with a red light intensity of 100 μmol/m2-s. Overall, blue light with an intensity of 300 μmol/m2-s and red light with an intensity of 100 μmol/m2-s were found to be the most efficient at removing carbon and nutrients. The results suggested that the color and intensity of light influence algal-bacterial growth and wastewater treatment efficiency.

Effect of environmental and nutritional conditions on the formation of single and mixed-species biofilms and their efficiency in cadmium removal

Remediation of contaminated water and wastewater using biosorption methods has attracted significant attention in recent decades due to its efficiency, convenience and minimised environmental effects. Bacterial biosorbents are normally deployed as a non-living powder or suspension. Little is known about the mechanisms or rates of bacterial attachment to surfaces and effect of various conditions on the biofilm development, as well as efficiency of living biofilms in the removal of heavy metals. In the present study, the effect of environmental and nutritional conditions such as pH, temperature, concentrations of phosphate, glucose, amino acid, nitrate, calcium and magnesium, on planktonic and biofilm growth of single and mixed bacterial cultures, were measured. Actinomyces meyeri, Bacillus cereus, Escherichia coli, Pseudomonas fluorescens strains were evaluated to determine the optimum biofilm growth conditions. The Cd(II) biosorption efficiencies of the mixed-species biofilm developed in the optimum growth condition, were investigated and modelled using Langmuir, Freundlich and Dubnin Radushkevich models. The biofilm quantification techniques revealed that the optimum concentration of phosphate, glucose, amino acid, nitrate, calcium and magnesium for the biofilm development were 25, 10, 1, 1.5, 5 and 0.5 g L−1, respectively. Further increases in the nutrient concentrations resulted in less biofilm growth. The optimum pH for the biofilm growth was 7 and alkaline or acidic conditions caused significant negative effects on the bacterial attachment and development. The optimum temperatures for the bacterial attachment to the surface were between 25 and 35 °C. The maximum Cd(II) biosorption efficiency (99%) and capacity (18.19 mg g−1) of the mixed-species biofilm, occurred on day 35 (Ci = 0.1 mg L−1) and 1 (Ci = 20 mg L−1) of biofilm growth, respectively. Modelling of the biosorption data revealed that Cd(II) removal by the living biofilm was a physical process by a monolayer of biofilm. The results of present study suggested that environmental and nutritional conditions had a significant effect on bacterial biofilm formation and its efficiency in Cd(II) removal.

Self-flocculation of enriched mixed microalgae culture in a sequencing batch reactor.

Microalgae-based biodiesel has gained widespread interest as an alternative energy source. Low-cost microalgae harvesting technologies are important for economically feasible biodiesel production. This study investigated, for the first time, the impact of adaptation period and height to diameter (H/D) ratio of a reactor on the growth and self-flocculation of microalgae, without the addition of bacteria. Six reactors were grouped into three sets of experiments, and each reactor was operated for 30 days at similar operating conditions (volume exchange ratio = 25% and settling time = 30 min). In set 1, two 8-L reactors, H5a (H/D ratio: 5) and H8a (H/D ratio: 8), were operated under batch operation. In set 2, reactors H5b and H8b were operated as sequential batch reactors (SBRs) without an adaptation period. In set 3, the reactors H5c and H8c were operated as SBRs with an adaptation period. The findings showed a threefold improvement in biomass productivity for the higher H/D ratio (H8c) and a reduction in biomass loss for microalgae. The H8c reactor exhibited 95% settling efficiency within 5 days, in comparison to 30 days for the H5c reactor. This study demonstrated that a higher H/D ratio and the introduction of an adaptation period in SBR operation positively influences growth and self-flocculation of enriched mixed microalgae culture.

Carbon-dependent growth, community structure and methane oxidation performance of a soil-derived methanotrophic mixed culture.

Soil-borne methane-oxidizing microorganisms act as a terrestrial methane (CH4) sink and are potentially useful in decreasing global CH4 emissions. Understanding the ecophysiology of methanotrophs is crucial for a thorough description of global carbon cycling. Here, we report the in situ balance of soils from abandoned landfills, meadows and wetlands, their capacities to produce and oxidize CH4 at laboratory-scale and the isolation of a soil-borne methanotrophic-heterotrophic mixed culture that was used for carbon (C1 and C2) feeding experiments. We showed that even with similar soil properties, the in situ CH4 balance depends on land-use. Different soils had different potentials to adapt to increased CH4 availability, leading to the highest CH4 oxidation capacities for landfill and wetland soils. The most efficient mixed culture isolated from the landfill was dominated by the methanotrophs Methylobacter sp. and Methylosinus sp., which were accompanied by Variovorax sp. and Pseudomonas sp. and remained active in oxidizing CH4 when supplied with additional C-sources. The ratios between type I and type II methanotrophs and between methanotrophic and heterotrophic bacteria changed when C-sources were altered. A significant effect of the application of the mixed culture on the CH4 oxidation of soils was established but the extent varied depending on soil type.

1,3-Propanediol production from glycerol in polyurethane foam containing anaerobic reactors: performance and biomass cultivation and retention.

The use of batch and upflow anaerobic reactors filled with polyurethane foam for pure glycerol fermentation was evaluated. The best reactor operational conditions to obtain high yield and productivity of 1,3-propanediol (1,3-PDO) as the main product and the role of the polyurethane foam in the growth and retention of suspended and attached biomass in the reactors were investigated. In the experiment at 30°C with a batch reactor (700mL), biomass growth was mostly as immobilized attached cells, and the achieved 1,3-PDO yield was up to 0.58molmol-gly-1. In the experiment (30°C) with an upflow anaerobic reactor (717mL), glycerol loading rates (gly-LR) ranging from 6.94 to 15.47g glyL-1day-1 were applied during a 102-day period. During the operation, average 1,3-PDO yield was 0.47molmol-gly-1, reaching a maximum of 0.51molmol-gly-1 at gly-LR of 13.57g glyL-1day-1. High 1,3-PDO productivity (5.35 to 5.44gL-1day-1) was obtained when gly-LR was 13.57 to 15.47g glyL-1day-1. Comparing the close yield values in both batch and continuous reactors and based on microbial evaluation, it is concluded that most of the 1,3-PDO generated in the continuous reactor was due to the suspended biomass retained by the foam cubes. The Clostridium genus was the predominant 1,3-PDO producer. Good yields and productivities with packed reactors were attributed to polyurethane foam used for mixed culture growth and retention. Consequently, they are worth considering for 1,3-PDO production from pure glycerol.

Exploiting collateral sensitivity controls growth of mixed culture of sensitive and resistant cells and decreases selection for resistant cells in a cell line model

BackgroundCDK4/6 inhibitors such as ribociclib are becoming widely used targeted therapies in hormone-receptor-positive (HR+) human epidermal growth factor receptor 2-negative (HER2−) breast cancer. However, cancers can advance due to drug resistance, a problem in which tumor heterogeneity and evolution are key features.MethodsRibociclib-resistant HR+/HER2− CAMA-1 breast cancer cells were generated through long-term ribociclib treatment. Characterization of sensitive and resistant cells were performed using RNA sequencing and whole exome sequencing. Lentiviral labeling with different fluorescent proteins enabled us to track the proliferation of sensitive and resistant cells under different treatments in a heterogeneous, 3D spheroid coculture system using imaging microscopy and flow cytometry.ResultsTranscriptional profiling of sensitive and resistant cells revealed the downregulation of the G2/M checkpoint in the resistant cells. Exploiting this acquired vulnerability; resistant cells exhibited collateral sensitivity for the Wee-1 inhibitor, adavosertib (AZD1775). The combination of ribociclib and adavosertib achieved additional antiproliferative effect exclusively in the cocultures compared to monocultures, while decreasing the selection for resistant cells.ConclusionsOur results suggest that optimal antiproliferative effects in heterogeneous cancers can be achieved via an integrative therapeutic approach targeting sensitive and resistant cancer cell populations within a tumor, respectively.

Impact of pomegranate peel as prebiotic in bio-yoghurt

PurposeThe effect of pomegranate whole and inside peels before and after extraction of the tannic acid have been carried out in stimulated media and in gastrointestinal conditionsDesign/methodology/approachAdding pomegranate peels with and without tannins at different levels to bio-stirred yoghurt to study its effect as prebiotic, in addition to evaluating the effect on physiochemical, sensorial and rheological propertiesFindingsThe results reveal that pomegranate peels before and after removing tannins had no effect on the viability of a single strain of Lb. acidophilus in stimulated media, while the growth of mixed probiotic culture (Lb.acidophilus and Bifidobacterium bifidum) was enhanced when pomegranate peels (whole and inside part) free from tannins were used. Tannin-free pomegranate peels enhanced the viability of probiotic culture under gastrointestinal conditions. In this study, all probiotic cultures were maintained counts around log 8 cfu /g in stirred bio-yoghurt supplements with pomegranate peels after 21days. Bio-yoghurt supplemented with pomegranate peels at 0.5% gained high scores for overall acceptability.Originality/valuePomegranate has been recognized as a good source of antioxidant and antimicrobial activities. Some researchers have utilized pomegranate peel in fermented milk, but most of the studies have found that tannins inhibit the bacterial culture. This study recommended that the supplementation of low-fat bio-yoghurt with tannin-free pomegranate peels enhanced the texture properties, viscosity of the product, as well as the viability of probiotic culture during shelf life. Therefore, the tannin-free pomegranate peel could be used as a prebiotic in functional fermented dairy products.

A Cross-sectional Study of Group B Streptococcus–Associated Sepsis, Coinfections, and Antibiotic Susceptibility Profile in Neonates in Pakistan

Neonatal sepsis is a leading cause of morbidity and early-life mortality worldwide, and previous data have reported the highest neonatal mortality rate in Pakistan. The present study aimed to decipher the prevalence of group B Streptococcus (GBS)-associated sepsis, coinfections, and antibiotic susceptibility of isolated microbes in neonates. Blood samples of 100 cases of neonatal sepsis were subcultured on blood agar, GBS agar, and MacConkey agar for isolation of GBS and suspected microbes. Of 100 neonatal blood samples, 85 blood samples were culture-positive, including mixed culture growth (n = 18), 25 samples as early-onset neonatal sepsis (EONS) and 60 as late-onset neonatal sepsis (LONS). Staphylococcus aureus showed high percent positivity (31.4%), followed by Candida sp (16.5%), GBS (14.1%), Klebsiella (14.1%), Staphylococcus epidermidis (11.8%), Pseudomonas (9.4%), Acinetobacter (9.4%), Esherichia coli (8.2%), and Enterococcus (5.9%). GBS was isolated more frequently from EONS than from LONS with 50% coinfections. Mode of delivery, gender, and respiratory distress in neonates were significantly associated with culture-positive sepsis. GBS isolates were highly (91.7%) susceptible to vancomycin, cefotaxime, and chloramphenicol, followed by penicillin (83.3%), ampicillin, and tetracycline (75%). GBS isolates were resistant to erythromycin, clindamycin, ciprofloxacin, and linezolid. Our findings evidenced GBS-associated risk factors and antibiotic susceptibility pattern of neonatal sepsis, which will help clinicians in management, control, and treatment of neonatal sepsis. The epidemiological evidence of GBS-associated neonatal sepsis, demographic characteristics, risk factor data analysis, and drug resistance pattern has disease prevention implications in neonates in low-income countries including Pakistan.

Predicting microbial growth in a mixed culture from growth curve data

Determining the fitness of specific microbial genotypes has extensive application in microbial genetics, evolution, and biotechnology. While estimates from growth curves are simple and allow high throughput, they are inaccurate and do not account for interactions between costs and benefits accruing over different parts of a growth cycle. For this reason, pairwise competition experiments are the current "gold standard" for accurate estimation of fitness. However, competition experiments require distinct markers, making them difficult to perform between isolates derived from a common ancestor or between isolates of nonmodel organisms. In addition, competition experiments require that competing strains be grown in the same environment, so they cannot be used to infer the fitness consequence of different environmental perturbations on the same genotype. Finally, competition experiments typically consider only the end-points of a period of competition so that they do not readily provide information on the growth differences that underlie competitive ability. Here, we describe a computational approach for predicting density-dependent microbial growth in a mixed culture utilizing data from monoculture and mixed-culture growth curves. We validate this approach using 2 different experiments with Escherichia coli and demonstrate its application for estimating relative fitness. Our approach provides an effective way to predict growth and infer relative fitness in mixed cultures.

Effect of quorum-quenching bacterium Bacillus sp. QSI-1 on protein profiles and extracellular enzymatic activities of Aeromonas hydrophila YJ-1

BackgroundIn natural environments, bacteria always live in communities with others where their physiological characteristics are influenced by each other. Bacteria can communicate with one another by using autoinducers. The current knowledge on the effect of quenching bacteria on others is limited to assess the impact of quorum-quenching bacterium Bacillus sp. QSI-1 on proteins pattern and virulence factors production of Aeromonas hydrophila YJ-1. Proteomic analysis was performed to find out protein changes and virulence factors, after 24 h co-culture.ResultsResults showed that several proteins of A. hydrophila YJ-1 were altered, seventy-two differentially expressed protein spots were excised from 2-DE gels and analyzed by MALDI-TOF/TOF MS, resulting in 63 individual proteins being clearly identified from 70 spots. Among these proteins, 50 were divided into 22 classes and mapped onto 18 biological pathways. Mixed-culture growth with Bacillus sp. QSI-1 resulted in an increase of A. hydrophilia proteins involved in RNA polymerase activity, biosynthesis of secondary metabolites, flagellar assembly, and two-component systems. In contrast, mixed culture resulted in a decreased level of proteins involved in thiamine metabolism; valine, leucine and isoleucine biosynthesis; pantothenate and CoA biosynthesis. In addition, the two extracellular virulence factors, proteases and hemolysin, were significantly reduced when A. hydrophila was co-cultured with QSI-1, while only lipase activity was observed to increase.ConclusionsThe information gathered from our experiment showed that Bacillus sp. QSI-1 has a major impact on the expression of proteins, including virulence factors of A. hydrophila.

Efficacy of a Ruminal Bacteriocin Against Pure and Mixed Cultures of Bovine Mastitis Pathogens.

Bacteriocins have been suggested as an alternative to conventional antibiotics for the prevention and treatment of mastitis infections. Predominant bacteria associated with bovine mastitis (n = 276 isolates) were evaluated for their susceptibility to bovicin HC5, a ruminal bacteriocin produced by Streptococcus equinus HC5. Bovicin HC5 inhibited most (> 80%) of the streptococcal and staphylococcal strains tested, but showed no effect against Escherichia coli strains. Susceptibility and resistance testing indicated that approximately 95% of the S. aureus strains were inhibited by concentrations of bovicin HC5 varying from 40 to 2560AUml-1. Bovicin HC5 (62.50AUml-1) also inhibited the growth of aerobic and anaerobic mixed cultures of S. aureus and S. agalactiae, but the combination with 0.25mmoll-1 of EDTA showed even greater bactericidal activity. These results demonstrate that bovicin HC5 is effective against the most prevalent pathogens found in contagious udder infections and could complement the use antibiotics in mastitis prophylaxis and therapy.

Mixed bacterial responses to dust exposure in an A549 eukaryotic co-culture.

Recent studies evaluated the impact of dust exposure on pure and mixed cultures of Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae, and Pseudomonas aeruginosa, revealing increased biofilm formation and altered sensitivities to H2O2. In this study, we examined the impact of lead (Pb), house, road, and combined dust on K. pneumoniae and P. aeruginosa in pure, mixed, or eukaryotic co-culture with human alveolar basal epithelial (A549) cells. Although no impact on pure or mixed culture growth was observed when bacteria were exposed to Pb, house, or road dust, increased biofilm was produced by P. aeruginosa in the presence of 0.8μg/mL of Pb, while P. aeruginosa and K. pneumoniae both exhibited increased biofilm production in the presence of 100μg/mL of house, road, and combined dust. When co-cultured with eukaryotic A549 cells, both bacteria demonstrated increased proliferation 6h post-infection when challenged with house, road, or combined dust. However, when mixed bacteria were co-cultured with A549 cells, P. aeruginosa exhibited a significant ~ 1.5-fold increased proliferation in the presence of 100μg/mL house, road, or combined dust. In sharp contrast, K. pneumoniae exhibited significantly reduced proliferation, when in mixed (with P. aeruginosa) A-549 co-culture, following exposure to 100μg/mL house, road, or combined dust. To evaluate whether a host cell inflammatory response contributed to this disparity, NF-κB activation was evaluated in each co-culture infection. K. pneumoniae-A-549 co-culture, treated with 100μg/mL of combined dust, exhibited no alterations in NF-κB translocation to the nucleus. Further, no differences in cytokine production were observed in the K. pneumoniae A-549 co-culture treated with 100μg/mL of house dust. Taken together, these data suggest that within the lung environment, mixed infections exposed to dust or dust contaminants could benefit one organism at the expense of the other, independent of the activation of inflammatory pathways.

Responses of the native species Sparganium angustifolium and the invasive species Egeria densa to warming and interspecific competition.

Climate change, especially warming temperatures, may increase invasion and modify the ecological impacts of invasive species by enhancing their ability to compete. To test the effects of warming on invasive plants, a mesocosm experiment was conducted to study competition between the invasive plant Egeria densa and the native hygrophyte Sparganium angustifolium under simulated warming conditions in a greenhouse. These two species were grown in monoculture (no competitor control) or mixed culture (competitor control) for two months under different temperature conditions (warming treatment or no-warming treatment). In S. angustifolium, the higher temperatures led to a shorter root length and significantly increased the aboveground traits of ramets, the total biomass, and the RGR (relative growth rate) but had no effect on the aboveground traits of genets. Growth in mixed culture significantly decreased the S. angustifolium ramet height under warmer conditions and significantly reduced the ramet root length, ramet number, genet biomass, root-to-shoot ratio and RGR of S. angustifolium under natural temperature conditions. All the morphological, biomass and growth traits of E. densa except for the root-to-shoot ratio were significantly increased by the warmer temperatures and decreased by growth in mixed culture. The RCI and RII of E. densa in both the no-warming and warmer environments were two and three times greater than those of S. angustifolium, whereas the ACI values for the two species were similar. Thus, S. angustifolium was a better competitor than E. densa under both temperature conditions. These results suggest that although the superior competitive ability of native species can inhibit E. densa growth, the performance of this species will be enhanced under future climate warming in cold regions.