Journal: mBio

Article Title: Cyanide Production by Chromobacterium piscinae Shields It from Bdellovibrio bacteriovorus HD100 Predation

doi: 10.1128/mBio.01370-17

Figure Lengend Snippet: (A) Impact of the media on predation of C. piscinae by B. bacteriovorus HD100. Control cultures (unpredated) and predated cultures are indicated by the letters C and P, respectively, after the medium. A predator-to-prey ratio (PPR) of approximately 0.03 was used. Values are means plus standard deviations (error bars). This experiment was repeated eight times. (B) Filter-sterilized supernatants from C. piscinae grown in DNB protect E. coli MG1655 from predation by B. bacteriovorus HD100. Supernatants from C. piscinae cultures incubated for 24 h in HEPES or DNB were tested. The initial E. coli viability and unpredated and predated E . coli viability are shown. A PPR of approximately 0.03 was used. Values that are not statistically significantly different ( P < 0.05) are indicated by the same letter (letter a or b). This experiment was repeated three times. (C) Correlation between the C. piscinae growth in DNB and the inhibitory activity with E. coli as the prey. At each time point, a sample of the C. piscinae culture was taken to measure the OD 600 . The cells within another aliquot were removed by filtration, and the inhibitory activity of the supernatant was assessed in predation tests with E. coli MG1655 as the prey. The results show a good correlation between the growth of C. piscinae and the inhibitory activity of its supernatant. A PPR of approximately 0.02 was used. This experiment was repeated three times. (D) The inhibitory activity of the DNB supernatants is dose dependent. Cultures of C. piscinae grown in DNB for 24 h were filter sterilized. The supernatants were then diluted into HEPES, and their inhibitory activity was studied using E. coli MG1655 as the prey. The E. coli viabilities were measured after 24 h. The values for pairs of samples (predated and unpredated samples) were compared. Values that are significantly different are indicated by asterisks as follows: *, P < 0.05; **, P < 0.01; ***, P < 0.001. This experiment was repeated four times.

Article Snippet: The strains used in this study were Bdellovibrio bacteriovorus HD100 (DSMZ 50701), Chromobacterium piscinae LMG 3947, and E. coli MG1655 (ATCC 700926).

Techniques: Control, Incubation, Activity Assay, Filtration

Journal: mBio

Article Title: Cyanide Production by Chromobacterium piscinae Shields It from Bdellovibrio bacteriovorus HD100 Predation

doi: 10.1128/mBio.01370-17

Figure Lengend Snippet: (A) Structure of violacein, a known inhibitor of microfaunal predators, i.e., nematodes and protists. This compound is produced by various bacterial strains. (B) Violacein does not negatively impact predation. Both a preparation purified from cultures of C. piscinae and a commercially available violacein were tested. E. coli MG1655 was used as the prey for B. bacteriovorus HD100. The initial E. coli viability (Initial), viability of E. coli cultures exposed to DMSO for 24 h with or without predation (DMSO), and viability of E. coli cultures exposed to 20 mg/liter violacein (in DMSO) for 24 h with or without predation (Violacein) are shown. A PPR of approximately 0.03 was used. Values are means plus standard deviations (error bars). Values that are not statistically significantly different ( P < 0.05) are indicated by the same letter (letter a, b, or c). This experiment was repeated three times.

Article Snippet: The strains used in this study were Bdellovibrio bacteriovorus HD100 (DSMZ 50701), Chromobacterium piscinae LMG 3947, and E. coli MG1655 (ATCC 700926).

Techniques: Produced, Purification

Journal: mBio

Article Title: Cyanide Production by Chromobacterium piscinae Shields It from Bdellovibrio bacteriovorus HD100 Predation

doi: 10.1128/mBio.01370-17

Figure Lengend Snippet: (A) Cyanogenesis by cultures of C. piscinae grown in DNB. The C. piscinae growth results are the same as in Fig. 1C . This experiment was repeated three times. (Inset) Average cyanide concentrations seen after 24 h from 13 independent experiments. (B) Potassium cyanide inhibition of predation. E. coli MG1655 was used as the prey strain. The surviving prey populations were determined after 24 h. The results show that cyanide concentrations of 50 µM and higher significantly inhibit predation. Statistical analyses were performed against the no-cyanide control samples. A PPR of approximately 0.03 was used. The values for pairs of values (predated and unpredated samples) were compared. Values that are significantly different are indicated by asterisks as follows: *, P < 0.05; **, P < 0.01; ***, P < 0.001. The experiment was performed four times. (C) B. bacteriovorus HD100 numbers after predation in the presence of cyanide. The population was determined using the cultures after 24 h from panel B, confirming that cyanide concentrations of 100 µM and higher significantly inhibit predation. Values that are not statistically significantly different ( P < 0.05) are indicated by the same letter (letter a, b, or c). This experiment was repeated four times. (D) Purging of the supernatant ( n = 3) or treating it with hydroxocobalamin ( n = 4) restores the ability of B. bacteriovorus HD100 to attack. E. coli MG1655 was used as the prey. The medium was treated for 1 h prior to the predation experiment was performed. The values were compared to the values for the untreated control samples. The viabilities of both the predator and prey were determined after 24 h. The values were compared to the value for the respective initial populations. Values that are significantly different are indicated by asterisks as follows: **, P < 0.01; ***, P < 0.001. ND*, not detected (<10 3 CFU/ml).

Article Snippet: The strains used in this study were Bdellovibrio bacteriovorus HD100 (DSMZ 50701), Chromobacterium piscinae LMG 3947, and E. coli MG1655 (ATCC 700926).

Techniques: Inhibition, Control

Journal: mBio

Article Title: Cyanide Production by Chromobacterium piscinae Shields It from Bdellovibrio bacteriovorus HD100 Predation

doi: 10.1128/mBio.01370-17

Figure Lengend Snippet: (A) Cyanide is mildly, yet significantly, toxic to attack-phase B. bacteriovorus HD100. B. bacteriovorus cultures were exposed to different micromolar concentrations of cyanide for 24 h, after which the viable populations were determined. A total of 12 independent cultures were tested. Each symbol represents the value for one culture, and the average result for a particular cyanide concentration is indicated by a light gray circle. Values were compared to the value for the no-cyanide control samples. Values that are significantly different ( P < 0.001) are indicated (***). This experiment was repeated 12 times. (B) Cyanide prevents release of the predatory cells from the bdelloplast. This graph shows the numbers of viable predators, which include both free-swimming predators and those within the bdelloplast, seen during and after a single predation event. The relative number illustrates the titer burst seen when lysis of the bdelloplast occurs. This experiment was repeated six times. (C) Confocal microscopic images showing the impact of cyanide on the development of the predatory cells within the bdelloplasts. E. coli MG1655 prey express the red fluorescent protein (red), while the predator is expressing the Venus yellow fluorescent protein (green). In the presence of 200 µM cyanide, elongation and development of the intraperiplasmic predatory cells, and the resulting lysis of the bdelloplast, are halted. This agrees with the results shown in panel B. The 0-h image was taken just prior to introducing the predatory strain. Bars = 10 µm.

Article Snippet: The strains used in this study were Bdellovibrio bacteriovorus HD100 (DSMZ 50701), Chromobacterium piscinae LMG 3947, and E. coli MG1655 (ATCC 700926).

Techniques: Concentration Assay, Control, Lysis, Expressing

Journal: Scientific Reports

Article Title: Bdellovibrio bacteriovorus Inhibits Staphylococcus aureus Biofilm Formation and Invasion into Human Epithelial Cells

doi: 10.1038/srep03811

Figure Lengend Snippet: (A) The prey spectrum of B. bacteriovorus HD100. Each prey was incubated in DNB medium in the presence or absence of the predator and the OD 600 was measured after 24 h. A decreased OD 600 in the presence of the predator was indicative that this prey was predated upon. The pathogenic prey evaluated are S. enterica (Se), Y. bercovieri (Yb), Y. enterocolitica (Ye), Y. pseudotuberculosis (Yp), Y. rohdei (Yr), A. baumannii (Ab), a clinical isolate of A. baumannii (Ab-CI) and S. aureus (Sa) (* p < 0.05, ** p < 0.01, *** p < 0.001). The initial OD 600 value of each culture was: 0.18, 0.17, 0.17, 0.18, 0.15, 0.25, 0.25 and 0.4, respectively. (B) Prevention of S. aureus biofilm formation using culture supernatant from host-independent B. bacteriovorus HD100 (HIB). The supernatant was added (10%) to the S. aureus culture in 96-well plates. For the control wells, 10% fresh PYE medium was added (*** = P < 0.001). (C) Effect of different concentrations of Proteinase K on S. aureus -biofilm formation in 96 well plates. Proteinase K was serially diluted in PYE medium and added (10%) to the S. aureus culture in 96-well plates (a, b, c, and d = P < 0.05). (D) HIB culture supernatants have no effect on S. aureus growth. Fresh S. aureus cultures were diluted 100-fold in TSB medium supplemented with 10% fresh PYE or HIB supernatant in 96 well plates. The plate was incubated at 37°C with frequent shaking and S. aureus growth (OD 600 ) was monitored over 12 h.

Article Snippet: Wild-type host dependant Bdellovibrio bacteriovorus HD100 (HDB) was purchased from the German Collection of Microorganisms and Cell Cultures (DSMZ).

Techniques: Incubation, Control