Effect of Fe on inorganic polyphosphate level in autotrophic and heterotrophic cells of Rhodospirillum rubrum.

Inorganic polyphosphate is involved in metal homeostasis in microorganisms. The aim of the study was to reveal differences in polyphosphate metabolism of Rhodospirillum rubrum under autotrophic and heterotrophic cultivation in the presence of Fe (2.3 mg Fe3+ L-1) and without Fe (traces). Heterotrophic conditions without Fe resulted in cell lysis and low biomass yield. High polyphosphate content and low exopolyphosphatase activity were observed in the cells cultivated autotrophically in the presence of Fe. The cells grown heterotrophically in the presence of Fe contained more phosphate and low-molecular polyphosphate; on the contrary, the content of the high molecular polyphosphate decreased in parallel with the increase in exopolyphosphatase activity. The possible involvement of Pi and polyphosphate to the formation of Fe-containing inclusions is discussed.

Effects of combined magnetic fields on bacteria Rhodospirillum rubrum VKM B-1621.

Bacteria are the simplest model of living organisms and thus are a convenient object for magnetobiological research. This paper describes some effects of combined magnetic fields (CMFs) on the bacterium Rhodospirillum rubrum strain VKM B-1621, which is not a pathogen but was selected due to its wide spectrum of growth abilities. The authors chose magnetic field-resonant phosphorus and iron (Fe3+ ) because P-containing biochemical compounds (standard abbreviations PP1 , AMP, ADP, ATP) provide energy flows in bacteria while iron could take part in formation of magnetosensitive intracellular inclusions. CMFs were produced by interaction of a geomagnetic field (ВDС ) and an alternating electromagnetic field (ВАС ), which were similar in their intensities. Their magnetic characteristics were as follows: (CMF-1) ВDC = 46.80 µÐ¢, ВАС = 86.11 µT, f = 807.0 Hz; (CMF-2) ВDC = 46.80 µÐ¢, ВАС = 86.11 µT, f = 38.3 Hz; that is, the frequencies of applied alternating electromagnetic fields coincided with cyclotron frequencies of phosphorus or ferric ions, respectively. The blank variants were exposed to the geomagnetic field. The CMFs increased bacterial consumption of dissolved iron as measured by residual concentrations of iron in the medium (P > 99%). An increase of bacterial nitrate reduction in the CMFs was statistically insignificant (P > 90%) when measured by residual concentrations of nitrate. Application of CMFs can influence bacterial activity and metabolism. Bioelectromagnetics. 2018;39:485-490, 2018. © 2018 Wiley Periodicals, Inc.

The biosorption of cadmium and cobalt and iron ions by yeast Cryptococcus humicola at nitrogen starvation.

Yeasts Cryptococcus humicola accumulated cadmium, cobalt, and iron (~ 50, 17, and 4% of the content in the medium, respectively) from the medium containing glucose, phosphate, and 2 mmol/L of metal salts. The effects of metal absorption on the levels of orthophosphate (Pi) and inorganic polyphosphate (polyP) varied for the metals under study. The levels of Pi and polyP increased in the case of cadmium and cobalt, respectively. In the case of iron, no changes in the levels of Pi and polyP were observed. Multiple DAPI-stained polyP inclusions were observed in the cytoplasm of cadmium-containing cells. The intensity of DAPI staining of the cell wall especially increased in case of cobalt and iron accumulation.

Application of static and impulse magnetic fields to bacteria Rhodospirillum rubrum VKM B-1621.

The paper presents effects of different magnetic fields (MFs) (static-SMF and impulse-IMF) on bacteria Rhodospirillum rubrum VKM B-1621. The MFs had different magnetic strength: SMF-up to 173 mT; IMF-25 mT. The studied object was amylase activity which was measured by decrease in the starch concentration during incubation in the MFs. The term of incubation in the MFs was limited with 2 h. The SMF affected neither amylase activity of R. rubrum nor standard deviation in distribution of the residual starch concentration along the plate but the IMF did. The IMS effects varied along the plate which could be related with distance from the magnetic center of the applied device. In whole, application of impulse MFs can regulate bacterial activity and thus could be used for biotechnological application.