Novel L-amino acid oxidase with algicidal activity against toxic cyanobacterium Microcystis aeruginosa synthesized by a bacterium Aquimarina sp

A brownish yellow pigmented bacterial strain, designated antisso-27, was recently isolated from a water area of saltpan in Southern Taiwan. Phylogenetic analyses based on 16S rRNA gene sequences indicate that strain antisso-27 belongs the genus Aquimarina in the family Flavobacteriacea and its only closest neighbor is Aquimarina spongiae (96.6%). Based on screening for algicidal activity, strain antisso-27 exhibits potent activity against the toxic cyanobacterium Microcystis aeruginosa. Both the strain antisso-27 bacterial culture and its culture filtrate show algicidal activity against the toxic cyanobacterium, indicating that an algicidal substance is released from strain antisso-27. The algicidal activity of strain antisso-27 occurs during the late stationary phase of bacterial growth. Strain antisso-27 can synthesize an algicidal protein with a molecular mass of 190 kDa, and its isoelectric point is approximately 9.4. This study explores the nature of this algicidal protein such as l-amino acid oxidase with broad substrate specificity. The enzyme is most active with l-leucine, l-isoleucine, l-methionine and l-valine and the hydrogen peroxide generated by its catalysis mediates algicidal activity. This is the first report on an Aquimarina strain algicidal to the toxic M. aeruginosa and the algicidal activity is generated through its enzymatic activity of l-amino acid oxidase.     

The effect of nutrient additions on bacterial activity in seagrass (Posidonia oceanica) sediments

The influence of nutrient additions on benthic bacterial activity under seagrass meadows was tested by enriching five seagrass (Posidonia oceanica) meadows with nutrients over one year. We found a highly significant response of benthic bacterial activity to nutrient additions, which was reflected in greater (about two-fold) ammonification rates and, to a smaller extent, a significant tendency for a greater exoenzymatic activity. Nutrient additions significantly raised bacterial activity, without altering the seasonal changes in bacterial activity. As a result of the increased bacterial activity, the organic content of the sediments declined significantly, by about 33%, after one year of nutrient addition. Hence, nutrient additions to the seagrass meadows enhance seagrass production but also accelerate bacterial decomposition of seagrass carbon, thereby reducing the capacity of the sediments to store organic carbon. These results demonstrate that sediment nutrient availability limits bacterial activity in these Posidonia oceanica meadows, and identify bacteria as important nutrient consumers in these systems.     

The antibacterial activity of phospholipase A2 type IIA is regulated by the cooperative lipid chain melting behavior in Staphylococcus aureus

As one of its primary physiological functions, sPLA₂-IIA appears to act as an antibacterial agent. In particular, sPLA₂-IIA shows high activity towards Gram-positive bacteria such as Staphylococcus aureus (S. aureus). This antibacterial activity results from the preference of the enzyme towards membranes enriched in anionic lipids, which is a common feature of bacterial membranes. An intriguing aspect observed in a variety of bacterial membranes is the presence of a broad but cooperative lipid chain melting event where the lipids in the membrane transition from a solid-ordered (so) into a liquid-disordered (ld) state close to physiological temperatures. It is known that the enzyme is sensitive to the level of lipid packing, which changes sharply between the so and the ld states. Therefore, it would be expected that the enzyme activity is regulated by the bacterial membrane thermotropic behavior. We determine by FTIR the thermotropic lipid chain melting behavior of S. aureus and find that the activity of sPLA₂-IIA drops sharply in the so state. The activity of the enzyme is also evaluated in terms of its effects on cell viability, showing that cell survival increases when the bacterial membrane is in the so state during enzyme exposure. These results point to a mechanism by which bacteria can develop increased resistance towards antibacterial agents that act on the membrane through a cooperative increase in the order of the lipid chains. These results show that the physical behavior of the bacterial membrane can play an important role in regulating physiological function in an in vivo system.     

A Comparison of Effects of Broad-Spectrum Antibiotics and Biosurfactants on Established Bacterial Biofilms

Current antibiofilm solutions based on planktonic bacterial physiology have limited efficacy in clinical and occasionally environmental settings. This has prompted a search for suitable alternatives to conventional therapies. This study compares the inhibitory properties of two biological surfactants (rhamnolipids and a plant-derived surfactant) against a selection of broad-spectrum antibiotics (ampicillin, chloramphenicol and kanamycin). Testing was carried out on a range of bacterial physiologies from planktonic and mixed bacterial biofilms. Rhamnolipids (Rhs) have been extensively characterised for their role in the development of biofilms and inhibition of planktonic bacteria. However, there are limited direct comparisons with antimicrobial substances on established biofilms comprising single or mixed bacterial strains. Baseline measurements of inhibitory activity using planktonic bacterial assays established that broad-spectrum antibiotics were 500 times more effective at inhibiting bacterial growth than either Rhs or plant surfactants. Conversely, Rhs and plant biosurfactants reduced biofilm biomass of established single bacterial biofilms by 74–88 and 74–98 %, respectively. Only kanamycin showed activity against biofilms of Bacillus subtilis and Staphylococcus aureus. Broad-spectrum antibiotics were also ineffective against a complex biofilm of marine bacteria; however, Rhs and plant biosurfactants reduced biofilm biomass by 69 and 42 %, respectively. These data suggest that Rhs and plant-derived surfactants may have an important role in the inhibition of complex biofilms.     

Two Distinct Hemolytic Activities in Xenorhabdus nematophila Are Active against Immunocompetent Insect Cells

Xenorhabdus spp. and Photorhabdus spp. are major insect bacterial pathogens symbiotically associated with nematodes. These bacteria are transported by their nematode hosts into the hemocoel of the insect prey, where they proliferate within hemolymph. In this work we report that wild strains belonging to different species of both genera are able to produce hemolysin activity on blood agar plates. Using a hemocyte monolayer bioassay, cytolytic activity against immunocompetent cells from the hemolymph of Spodoptera littoralis (Lepidoptera: Noctuidae) was found only in supernatants of Xenorhabdus; none was detected in supernatants of various strains of Photorhabdus. During in vitro bacterial growth of Xenorhabdus nematophila F1, two successive bursts of cytolytic activity were detected. The first extracellular cytolytic activity occurred when bacterial cells reached the stationary phase. It also displayed a hemolytic activity on sheep red blood cells, and it was heat labile. Among insect hemocyte types, granulocytes were the preferred target. Lysis of hemocytes by necrosis was preceded by a dramatic vacuolization of the cells. In contrast the second burst of cytolytic activity occurred late during stationary phase and caused hemolysis of rabbit red blood cells, and insect plasmatocytes were the preferred target. This second activity is heat resistant and produced shrinkage and necrosis of hemocytes. Insertional inactivation of flhD gene in X. nematophila leads to the loss of hemolysis activity on sheep red blood cells and an attenuated virulence phenotype in S. littoralis (A. Givaudan and A. Lanois, J. Bacteriol. 182:107–115, 2000). This mutant was unable to produce the early cytolytic activity, but it always displayed the late cytolytic effect, preferably active on plasmatocytes. Thus, X. nematophila produced two independent cytolytic activities against different insect cell targets known for their major role in cellular immunity.     

Effect of Sheep Urine Deposition on the Bacterial Community Structure in an Acidic Upland Grassland Soil

The effect of the addition of synthetic sheep urine (SSU) and plant species on the bacterial community composition of upland acidic grasslands was studied using a microcosm approach. Low, medium, and high concentrations of SSU were applied to pots containing plant species typical of both unimproved (Agrostis capillaris) and agriculturally improved (Lolium perenne) grasslands, and harvests were carried out 10 days and 50 days after the addition of SSU. SSU application significantly increased both soil pH (P < 0.005), with pH values ranging from pH 5.4 (zero SSU) to pH 6.4 (high SSU), and microbial activity (P < 0.005), with treatment with medium and high levels of SSU displaying significantly higher microbial activity (triphenylformazan dehydrogenase activity) than treatment of soil with zero or low concentrations of SSU. Microbial biomass, however, was not significantly altered by any of the SSU applications. Plant species alone had no effect on microbial biomass or activity. Bacterial community structure was profiled using bacterial automated ribosomal intergenic spacer analysis. Multidimensional scaling plots indicated that applications of high concentrations of SSU significantly altered the bacterial community composition in the presence of plant species but at different times: 10 days after application of high concentrations of SSU, the bacterial community composition of L. perenne-planted soils differed significantly from those of any other soils, whereas in the case of A. capillaris-planted soils, the bacterial community composition was different 50 days after treatment with high concentrations of SSU. Canonical correspondence analysis also highlighted the importance of interactions between SSU addition, plant species, and time in the bacterial community structure. This study has shown that the response of plants and bacterial communities to sheep urine deposition in grasslands is dependent on both the grass species present and the concentration of SSU applied, which may have important ecological consequences for agricultural grasslands.     

Eggshell Bacterial Load Is Related to Antimicrobial Properties of Feathers Lining Barn Swallow Nests

The use of feathers to line bird’s nests has traditionally been interpreted as having a thermoregulatory function. Feather-degrading bacteria growing on feathers lining nests may have antimicrobial properties, which may provide an additional benefit to lining nests with feathers. We test the hypothesis that the production of antimicrobial substances by feather bacteria affects the microbiological environment of the nest, and therefore the bacterial density on eggshells and, indirectly, hatching success. These effects would be expected to differ between nests lined with pigmented and white feathers, because bacteria grow differently on feathers of different colors. We experimentally manipulated the composition of pigmented and unpigmented feathers in nests of the barn swallow (Hirundo rustica) and studied the antimicrobial properties against the keratin-degrading bacterium Bacillus licheniformis of bacteria isolated from feathers of each color. Analyzed feathers were collected at the end of the incubation period, and antimicrobial activity was defined as the proportion of bacteria from the feathers that produce antibacterial substances effective against B. licheniformis. Our experimental manipulation affected antimicrobial activity, which was higher in nests with only white feathers at the beginning of incubation. Moreover, white feathers showed higher antimicrobial activity than black ones. Interestingly, antimicrobial activity in feathers of one of the colors correlated negatively with bacterial density on feather of the opposite color. Finally, antimicrobial activity of white feathers was negatively related to eggshell bacterial load. These results suggest that antimicrobial properties of feathers in general and of white feathers in particular affect the bacterial environment in nests. This environment in turn affects the bacterial load on eggshells, which may affect hatching success.     

Interactions between Zeldia Punctata (Cephalobidae) and bacteria in the presence or absence of maize plants

Bacterial-feeding nematodes constitute one of the primary grazers of soil bacteria. We investigated the effects of selective grazing of a representative nematode (Zeldia punctata, Cephalobidae) on nematode life history and population biology and on the soil microbial community. Firstly, we measured (i) the effect of five different bacterial strains on the nematode life cycle using petri dishes and (ii) the impact of bacterial inoculation on nematode population growth in a soil microcosm. Selection of the five bacterial strains was based on morphology, cell-wall characteristics and mucus production. Z. punctata development was strongly affected by the type of bacteria ingested, independent of experimental design. Bacterial cell-wall characteristics seemed to directly affect Z. punctata development since high nematode densities were only reached with gram-negative strains (Pseudomonas monteilii and Methylobacterium nodulans). In petri dishes, the filamentous organisms (Actinomyces sp.) and mucus-producing bacteria (Bradyrhizobium sp.) led to the least reproduction. Duration of the various nematode life phases (egg, juvenile, reproductive stage and non-reproductive stage) was significantly affected by the bacterial food source. Total life span varied from 12.5 days (Bradyrhizobium sp.) to 40 days (Pseudomonas monteilii). Secondly, we monitored the influence of Z. punctata on the indigenous soil microbial community in the presence or absence of a maize plantlet. Nematode inoculation led to an increase in bacterial activity (as measured by alkaline phosphatase activity) but did not significantly influence bacterial biomass. The genetic fingerprint (DGGE) of soil bacteria was more influenced by plant presence than by nematode inoculation. Nematode activity has important repercussions on N flux in the soil since inoculation of Z. punctata in the absence of plants resulted in a net increase of N mineralization (2 mg N per pot) while a decrease of mineral N (0.5 mg N per pot) was observed in the absence of the nematodes, due to bacterial immobilization. This study underscores the close relationship between selective bacterial grazing and nematode development. Nevertheless, the impact of nematode grazing on the overall soil microbial community seems to primarily affect microbial activity and relative dominance rather than microbial diversity.     

Protein C Inhibitor—A Novel Antimicrobial Agent

Protein C inhibitor (PCI) is a heparin-binding serine proteinase inhibitor belonging to the family of serpin proteins. Here we describe that PCI exerts broad antimicrobial activity against bacterial pathogens. This ability is mediated by the interaction of PCI with lipid membranes, which subsequently leads to their permeabilization. As shown by negative staining electron microscopy, treatment of Escherichia coli or Streptococcus pyogenes bacteria with PCI triggers membrane disruption followed by the efflux of bacterial cytosolic contents and bacterial killing. The antimicrobial activity of PCI is located to the heparin-binding site of the protein and a peptide spanning this region was found to mimic the antimicrobial activity of PCI, without causing lysis or membrane destruction of eukaryotic cells. Finally, we show that platelets can assemble PCI on their surface upon activation. As platelets are recruited to the site of a bacterial infection, these results may explain our finding that PCI levels are increased in tissue biopsies from patients suffering from necrotizing fasciitis caused by S. pyogenes. Taken together, our data describe a new function for PCI in innate immunity.     

Up-regulation of circulating hemocyte population in response to bacterial challenge is mediated by octopamine and 5-hydroxytryptamine via Rac1 signal in Spodoptera exigua

Bacterial challenge induced a significant increase in the total hemocyte population within 4 h in the beet armyworm, Spodoptera exigua. Octopamine and 5-hydroxytryptamine (5-HT) are known to play critical roles in mediating insect immune responses. This study analyzed the effects of both biogenic monoamines on mediating up-regulation of circulating hemocyte population in response to bacterial challenge. Injection of either octopamine or 5-HT induced a significant increase in the total hemocyte count in the hemolymph without any bacterial challenge. On the other hand, the monoamine antagonists, phentolamine (an octopamine antagonist) and ketanserin (a 5-HT antagonist) each suppressed the increase of the circulating hemocyte counts in response to bacterial challenge. This rapid change of circulating hemocyte population did not appear to be the result of de novo hemocyte production from the hematopoietic organ because a physical block (“ligation”) of hemolymph circulation between thorax and abdomen did not inhibit the increase of hemocyte counts in the isolated abdomen in response to bacterial challenge. The effects of the two monoamines on hemocyte numbers were not dependent on the mediatory effects of eicosanoids, because dexamethasone, an eicosanoid biosynthesis inhibitor, had no effect on the hemocyte recruitment induced by the monoamines. On the other hand, an adenylate cyclase inhibitor, NKY80, significantly impaired hemocyte mobilization in response to bacterial challenge, implying involvement of cyclic AMP in the control of hemocyte numbers. Also, a Rac1 inhibitor, NSC23766, significantly antagonized the effects of monoamines in increasing circulating hemocyte numbers. Rac1 activity was necessary to form F-actins in the hemocytes of S. exigua, where its activity showed a quantitative correlation with hemocyte-spreading behavior. This study suggests that octopamine and 5-HT mediate a rapid increase of circulating hemocyte population in response to bacterial challenge via Rac1 signal in S. exigua.     

Isomerization of an Antimicrobial Peptide Broadens Antimicrobial Spectrum to Gram-Positive Bacterial Pathogens

The branched M33 antimicrobial peptide was previously shown to be very active against Gram-negative bacterial pathogens, including multidrug-resistant strains. In an attempt to produce back-up molecules, we synthesized an M33 peptide isomer consisting of D-aminoacids (M33-D). This isomeric version showed 4 to 16-fold higher activity against Gram-positive pathogens, including Staphylococcus aureus and Staphylococcus epidermidis, than the original peptide, while retaining strong activity against Gram-negative bacteria. The antimicrobial activity of both peptides was influenced by their differential sensitivity to bacterial proteases. The better activity shown by M33-D against S. aureus compared to M33-L was confirmed in biofilm eradication experiments where M33-L showed 12% activity with respect to M33-D, and in vivo models where Balb-c mice infected with S. aureus showed 100% and 0% survival when treated with M33-D and M33-L, respectively. M33-D appears to be an interesting candidate for the development of novel broad-spectrum antimicrobials active against bacterial pathogens of clinical importance.     

The contribution of acidulant to the antibacterial activity of acid soluble α- and β-chitosan solutions and their films

This study evaluated individual contributions of dissolving acids (acetic acid, lactic acid, and hydrochloric acid) or acid solubilized chitosan to the antibacterial activity against Listeria innocua and Escherichia coli as solutions and dried films. Solutions containing chitosan showed significantly (P?<?0.05) different inhibitory activity (measured as percentage of inhibition (PI), in percent) against L. innocua and E. coli, compared to equivalent acid solutions. This increase was calculated as additional inhibition (AI, in percent), which could be as high as 65 % in solutions containing 300–320 kDa chitosan depending on the acid type, bacterial species, and the chitosan form (α or β). Solutions containing 4–5 kDa chitosan had lower AI and showed much greater variability among the different chitosan forms, acid types, and bacterial species. Higher molecular weight (Mw) chitosan also showed significantly higher levels of adsorption to bacterial cells than that of lower Mw samples, suggesting that the observed increase in inhibition was the result of surface phenomena. The contribution of acids to the antibacterial activity of chitosan films was assessed by comparing non-rinsed and rinsed films (rinsed in the appropriate broth to remove residual acids and active fragments formed on the dried film). Rinsing β-chitosan films has reduced PI by as much as 28 % compared with non-rinsed films, indicating that part of the antibacterial activity of chitosan films is due to the presence of soluble acid compounds and/or other active fragments. Overall, both acidulant and chitosan were found to contribute to the antibacterial activity of acid solubilized α- and β-chitosan, with the exact antibacterial activity of chitosan varying based on the solution and film properties, suggesting a complex interaction.     

Molecular and biochemical characterization of a new endoinulinase producing bacterial strain of Bacillus safensis AS-08

Microbial inulinases are an important class of industrial enzymes, which are used for the production of fructooligosaccharides and high-fructose syrup. Endoinulinase producing bacterial strains were isolated from soil samples taken from the vicinity of Asparagus sp. root tubers. All the bacterial strains were screened for inulinase activity. The primary screening was carried out based on hydrolytic zone on agar plates containing inulin-based medium and Lugol’s iodine solution. Thus 30 inulinase producing bacterial strains were isolated. Out of 30 strains, 5 bacterial strains were found endoinulolytic, whereas 25 were exoinulolytic on the basis of action pattern of the enzyme. In tertiary screening, the bacterial isolate AS-08 was found to be most efficient for inulinase activity. Morphological, biochemical and physiological characteristics of the bacterial isolate AS-08 confirmed it as Bacillus sp. Furthermore, species-specific identification by 16S rDNA sequencing and phylogenetic analysis revealed the isolate as Bacillus safensis. Bacillus pumilus SH-B30 was found to be the nearest homolog. The strain showed maximum inulinase activity (12.56 U/mL) after 20 h of incubation at 37°C.     

Native and dry-heated lysozyme interactions with membrane lipid monolayers: Lipid packing modifications of a phospholipid mixture,model of the Escherichia coli cytoplasmic membrane

Antimicrobial resistance is currently an important public health issue. The need for innovative antimicrobials is therefore growing. The ideal antimicrobial compound should limit antimicrobial resistance. Antimicrobial peptides or proteins such as hen egg white lysozyme are promising molecules that act on bacterial membranes. Hen egg white lysozyme has recently been identified as active on Gram-negative bacteria due to disruption of the outer and cytoplasmic membrane integrity. Furthermore, dry-heating (7 days and 80 °C) improves the membrane activity of lysozyme, resulting in higher antimicrobial activity. These in vivo findings suggest interactions between lysozyme and membrane lipids. This is consistent with the findings of several other authors who have shown lysozyme interaction with bacterial phospholipids such as phosphatidylglycerol and cardiolipin. However, until now, the interaction between lysozyme and bacterial cytoplasmic phospholipids has been in need of clarification. This study proposes the use of monolayer models with a realistic bacterial phospholipid composition in physiological conditions. The lysozyme/phospholipid interactions have been studied by surface pressure measurements, ellipsometry and atomic force microscopy. Native lysozyme has proved able to absorb and insert into a bacterial phospholipid monolayer, resulting in lipid packing reorganization, which in turn has lead to lateral cohesion modifications between phospholipids. Dry-heating of lysozyme has increased insertion capacity and ability to induce lipid packing modifications. These in vitro findings are then consistent with the increased membrane disruption potential of dry heated lysozyme in vivo compared to native lysozyme. Moreover, an eggPC monolayer study suggested that lysozyme/phospholipid interactions are specific to bacterial cytoplasmic membranes.     

Antimicrobial activity of an abiotic host defense peptide mimic

Bacterial drug resistance is emerging as one of the most significant challenges to human health. Antimicrobial peptides (AMPs), which are produced by many tissues and cell types of invertebrates, insects, and humans, as part of their innate immune system, have attracted considerable interest as alternative antibiotics. Interest in novel mimics of AMPs has increased greatly over the last few years. This report details a new AMP mimic, based on phenylene ethynylene, with improved antimicrobial activity and selectivity. Screening against a large set of bacterial and other organisms demonstrates broad spectrum antimicrobial activity including activity against antibiotic resistant bacterial like methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE) as well as activity against yeast (Candida albicans) and fungus (Stachybotrys chartarum). Bacterial resistance development studies using Staphylococcus aureus show a rapid increase in MIC for conventional antibiotics, ciprofloxacin and norfloxacin. In sharp contrast, no change in MIC was observed for the AMP mimic. Cytotoxicity experiments show that the AMP mimic acts preferentially on microbes as opposed to mammalian red blood cells, 3T3 fibroblasts, and HEPG2 cells. In vivo experiments determined the maximum tolerated dose (MTD) to be 10 mg/kg suggesting a therapeutic window is available. These studies indicate that nonpeptidic amphiphilic AMP mimics could be developed as potential new treatments for antibiotic-resistant bacterial infections.     

Nitrogen uptake of Hypholoma fasciculare and coexisting bacteria

The white-rot fungus Hypholoma fasciculare coexists with a bacterial community that uses low-molecular weight carbon sources provided by fungal, extracellular enzyme activities. Since fungal development on wood is limited by the availability of nitrogen (N), bacteria could contribute to the N supply. To prove or disapprove an interaction in terms of N transfer, N sources of the fungus and the coexisting bacterial isolates were investigated, and the bacterial N₂ fixation was quantified. Fungal, fungal—bacterial and bacterial wood decomposition was analysed by Fourier transform infrared spectroscopy (FTIR), mass loss and surface pH. Microbial N preferences were investigated by elemental analysis isotope ratio mass spectrometry (IRMS). In addition, diazotrophic activity was explored after cultivation under a ¹⁵?N₂/O₂ atmosphere. Decomposition was similar with and without bacteria and both H. fasciculare and coexisting bacteria preferred reduced N species, such as urea, ammonium and organic N. In most of the bacteria, the ¹⁵?N abundance in the biomass increased significantly but to a low extent if they were cultivated under a ¹⁵?N₂/O₂ atmosphere. This effect is considered an artefact and attributed to adsorption rather than to bacterial N₂ fixation activity. Hence, the bacteria coexisting with H. fasciculare rather competed for the same N sources than supported fungal N supply by diazotrophic activity.     

Synergistic Antimicrobial Activity of Camellia sinensis and Juglans regia against Multidrug-Resistant Bacteria

Synergistic combinations of antimicrobial agents with different mechanisms of action have been introduced as more successful strategies to combat infections involving multidrug resistant (MDR) bacteria. In this study, we investigated synergistic antimicrobial activity of Camellia sinensis and Juglans regia which are commonly used plants with different antimicrobial agents. Antimicrobial susceptibility of 350 Gram-positive and Gram-negative strains belonging to 10 different bacterial species, was tested against Camellia sinensis and Juglans regia extracts. Minimum inhibitory concentrations (MICs) were determined by agar dilution and microbroth dilution assays. Plant extracts were tested for synergistic antimicrobial activity with different antimicrobial agents by checkerboard titration, Etest/agar incorporation assays, and time kill kinetics. Extract treated and untreated bacteria were subjected to transmission electron microscopy to see the effect on bacterial cell morphology. Camellia sinensis extract showed higher antibacterial activity against MDR S. Typhi, alone and in combination with nalidixic acid, than to susceptible isolates.” We further explore anti-staphylococcal activity of Juglans regia that lead to the changes in bacterial cell morphology indicating the cell wall of Gram-positive bacteria as possible target of action. The synergistic combination of Juglans regia and oxacillin reverted oxacillin resistance of methicillin resistant Staphylococcus aureus (MRSA) strains in vitro. This study provides novel information about antimicrobial and synergistic activity of Camellia sinensis and Juglans regia against MDR pathogens     

Upregulation of cellulase activity and mRNA levels by bacterial challenge in the earthworm Eisenia andrei,supporting the involvement of cellulases in innate immunity

To investigate whether earthworm cellulases contribute to the innate immune system, the responsiveness of cellulase activity and mRNA expression to bacterial challenge was examined by zymography and RNA sequencing. A zymographic analysis revealed that the activity levels of earthworm cellulases were upregulated in response to either a bacterial (Bacillus subtilis or Escherichia coli) or LPS challenge. After the challenge, significant increases in cellulase 1 and cellulase 2 activity levels were observed within 8–16 and 16–24 h, respectively. In the coelomic fluid, both activities were significantly upregulated at 8 h post-injection with B. subtilis. Based on RNA sequencing, cellulase-related mRNAs encoding beta-1,4-endoglucanases were upregulated by 3-fold within 6 h after B. subtilis injection. Our results clearly demonstrated that earthworm cellulases are upregulated by bacterial challenge at the mRNA and protein levels. These results support the view that earthworm cellulases act as inducible humoral effectors of innate immunity against bacterial infection.     

Differences in Bacterial Community Structure in Two Color Morphs of the Hawaiian Reef Coral Montipora capitata

Corals harbor diverse bacterial associations that contribute to the health of the host. Using 16S rRNA pyrosequencing, we compared the bacterial communities of red and orange morphs of the Hawaiian coral Montipora capitata. Although both color morphs shared dominant bacterial genera, weighted and unweighted UniFrac analyses showed distinct bacterial communities. A single operational taxonomic unit (OTU), classified as Vibrio, represented the largest driver of differences between the color morphs. This OTU comprised 35.4% (±5.5%) of the orange morph bacterial community yet comprised 1.1% (±0.6%) of the red morph bacterial community. Cultivable bacteria from the two color morphs were also compared and tested for antibacterial activity. Cultured isolates represented 14 genera (7% of the total genera identified from sequencing data), and all but two cultured isolates had a matching OTU from the sequencing data. Half of the isolates tested (8 out of 16) displayed antibacterial activity against other cultured isolates but not against two known bacterial pathogens of M. capitata. The results from this study demonstrate that the specificity of coral-bacterial associations extends beyond the level of coral species. In addition, culture-dependent methods captured bacterial diversity that was representative of both rare and abundant members of the associated bacterial community, as characterized by culture-independent methods.     

Identification and nematicidal activity of bacteria isolated from cow dung

Two hundred and nineteen bacterial strains were isolated from cow dung. Among these, 59 isolates displayed nematicidal activity against the model nematode Caenorhabditis elegans. Of the 59 bacterial strains, 17 killed >90 % of the tested nematodes within 1 h. Based on their 16S rRNA sequences, these 17 strains were identified as Alcaligenes faecalis, Bacillus cereus, Proteus penneri, Providencia rettgeri, Pseudomonas aeruginosa, Pseudomonas otitidis, Staphylococcus sciuri, Staphylococcus xylosus, Microbacterium aerolatum, Pseudomonas beteli. Among these 17 strains, 14 produced volatile organic compound(s) that inhibited the mobility of the C. elegans nematodes. These 14 strains also showed nematicidal activity against a plant pathogenic nematode Meloidogyne incognita. This is the first report demonstrating nematicidal activity for strains in genera Proteus, Providencia and Staphylococcus.