Figure 1.
Transmission electron microscopy (TEM) analysis of Vibrio sp. PS1.
In panels A–D, note the presence, in the nucleoid area, of the electron-dense inclusions about 10–50 nm in size exhibiting a polyhedral shape (arrows). Panels B and D are enlargement of regions of panels A and C, respectively. In panels E and F bacteria were grown in the presence of 31.2 µM deferoxamine that caused disassembly of the electron-dense inclusions with polyhedral shape and the appearance of leading to accumulation of electron-dense amorphous aggregates. Bars represent 1 µm in A and E, 0.5 µm in C and F, and 0.2 µm in B and D.
Figure 2.
Images of purified magnetic inclusions.
Purified magnetic inclusions were analyzed by scanning electron microscopy (SEM) (A) or transmission electron microscopy (TEM) (B). Note the tendency of the inclusions to stick together confirming their magnetic nature. Bars represent 0.1 µm in A and B.
Figure 3.
Light emission monitoring during growth of Vibrio sp. PS1.
In panels A–C, light emission of SMF-exposed (20, 200 or 2000 Gauss) or sham-exposed Vibrio sp. PS1 was monitored during growth on nutrient agar 1.5% containing 3% NaCl. In panel D bacteria were cultivated in the presence of 12 µM deferoxamine and SMF-exposed (2000 Gauss) or sham-exposed. In each panel data represent means values and standard deviations (bars) of at least three measurements of different cultures for each treatment. In panel E–F, light emission of SMF-exposed (2000 Gauss) or sham-exposed Vibrio sp. PS1 was monitored by photographs either in the absence (E) or the presence of 12 µM deferoxamine (F).
Figure 4.
Growth and viability of SMF-exposed and sham-exposed Vibrio sp. PS1.
Ten µl of a 1 O.D. (550 nm) suspension of Vibrio sp. PS1 were spotted at the centre of 3% NaCl nutrient agar plates and incubated at 18°C either in the absence (sham-exposed) or in the presence of SMF (2000 Gauss) (SMF-exposed). Bacteria were recovered at different time intervals and re-suspended in 1 ml of 3% NaCl nutrient broth. Growth and viability were evaluated by determining the O.D. (550 nm) (A), the number of CFU/ml (B) and by using a dead/live staining as detailed in the Materials and Methods section. Data are shown as mean ± standard deviation from at least three independent experiments.
Figure 5.
Transcript levels of luxA and regulatory genes.
Transcript levels of luxA (A), luxR (B), hfq (C), and VH02969, VH04846, VH05322 and VH05886 genes coding for Quorum Regulatory RNA (Qrr) (D) were measured in SMF-exposed or sham-exposed Vibrio sp. PS1 after 48 or 192 h of growth on nutrient agar 1.5% containing 3% NaCl. Results were normalized to 16S rRNA levels. Transcript levels of sham-exposed bacteria grown for 48 h are assumed equal to 1. Each real-time RT-PCR experiment was repeated three times using RNA samples extracted from replicated bacterial cultures for each treatment, and means and standard deviations (bars) were determined. Asterisks indicate statistically significant differences (p<0.01) between values of SMF-exposed and sham-exposed bacteria at the same time intervals.
Figure 6.
Transcript levels of type III secretion system (TTS)-encoding genes.
Transcript levels of TTS-encoding genes vopB, vopN and vscP were measured in SMF-exposed or sham-exposed Vibrio sp. PS1 after 48 or 192 h of growth on nutrient agar 1.5% containing 3% NaCl. Results were normalized to 16S rRNA levels. Transcript levels of sham-exposed bacteria grown for 48 h are assumed equal to 1. Each real-time RT-PCR experiment was repeated three times using RNA samples extracted from replicated bacterial cultures for each treatment, and means and standard deviations (bars) were determined. Asterisks indicate statistically significant differences (p<0.01) between values of SMF-exposed and sham-exposed bacteria at the same time intervals.
Figure 7.
Light emission monitoring during growth of V. harveyi strain BB120 and derivative mutants unable to synthesize the autoinducers CAI-1 or AI-2.
Harveyi clade Vibrio strain BB120 (A) and derivative mutants JMH603 (B), KM387 (C) and JAF633 (D) unable to synthesize, respectively, the autoinducers CAI-1, AI-2 and HAI-1 were SMF-exposed (2000 Gauss) or sham-exposed and light emission was monitored during growth on nutrient agar 1.5% containing 3% NaCl. In each panel data represent means values and standard deviations (bars) of at least three measurements.
Table 1.
Oligonucleotides used in this study.