Garbara, S.

Globa, L.

Gordienko, A.

Lesichkov, V.

English

Varna Medical University Press: Journals

E F F E C T O F C A 2 + AND A L 3 + IONS ON INTERACTION B E T W E E N BACTERIA AND MINERAL SORBENTS L . Globa, A . Gordienko, V. Lesichkov, S. Garbara Key-words: calcium ions — aluminium ions — bacteria — mineral sorbents Modern ways of water purification from microorganisms are not efficient enough because of their high aggregative and kinetic stability. The effect of remo­val of viruses and bacteria from water is increased by mineral sorbents during coagulation (1—3) and by their application as filters (4, 5). But there are still inadequate data about interaction between microorganisms and mineral sorbents. Heterocoagulation of admixture and water clarification (6, 7) is observed in acidic medium with negative values of С-potential of the mineral sorbent cells and particles being 20—30 mV. Coagulation of water admixtures with such wi­dely used agent as aluminium sulfate is strained under these conditions. Optimum water clarification with aluminium sulfate depends on the medium ionic composi­tion and is observed at pH 6,5—8,5 — isoelectric zone for aluminium hydroxide (1). At the same time bacterial interaction with mineral sorbents depends on the cation concentration and its type in the dispersion medium (8, 9). So we intended to study the effect of the medium cations on bacterial interac­tion with mineral sorbents for destabilization of microbe dispersions. Material and methods We used cultures Escherichia coli 163 and Streptococcus faecalis 134, culti­vated on meat — peptone agar at 37 °C for 24 hours. Cells were then washed 3 t i ­mes with distilled water in centrifuge at 6000 g for 15 minutes. Colloid solutions of montmorillonite and palygorskite were prepared by Sa-banin's method (10) from natural clays of Cherkassy deposit (USSR). Mineral fractions with particles « 1—2 mkm and < 1 mkm large were obtained by centrifugation. Interactions between bacteria and minerals were studied in solutions of cal­cium and aluminium chlorides. Three types of samples were prepared in each experiment: two signal ones — suspensions of bacteria and mineral (with par­ticles ~ 1—2 mkm large); test ones — suspensions of bacteria in the mineral colloid solutions (with particles being < 1 mkm large) of various concen­trations. Bacteria and mineral were shaked for 15 min. Bacteria concentra­tion remained the same — 5.107 cell/ml. Electrophoresis rate and С-potential of 50 cells of particles of mineral were determined using an apparatus for microelec­trophoresis (11). Preparations for electron microscopic research were done by negative contrasting of 2 % phosphatotungstic acid solutions (13). Effect of Ca 2 -f and A l 3 - ! - ions on..* Results and discussion Effect of the calcium ions content in dispersion medium on interaction of Str. faecalis cells and palygorskite was studied by microelectrophoresis. C-poten-tial of bacteria was found to be the same in calcium chloride solutions of 10~5— 10- 4 mol/1 at all the known concentrations of clay mineral (fig. 1). Further growth Fig . 1. £ —potential of Streptococcus faecalis 134 cells in colloid solutions of palygorskite with various concentrations (Cp) and the palygorskite particles (P) at the calcium chloride con-tent in the medium mol/1: (Д) — 10~5 ; (#) _ i c r 4 ; (O) — 10 3 Fig . 2. £ — potential of Escherichia coli 163 cells in colloid solutions of montmorillonite wi th various concentrations (См) and the montmorillonite particles (M) at the aluminium chloride content in the medium, mol/1: ( • ) — 10~ 6 ; (O) — 10 5 of calcium chloride content to 1 0 - 3 mol/1 slightly decrease the negative s-poten-tial of the mineral with practically no changes in c;-potential of bacteria. But transformations in the nature of their interaction bring about concentrational growth of palygorskite in the medium along with decrease of the negative ^-po­tential of microbes. Bacteria acquire С-potential which is characteristic of the mi­neral particles. Interaction of Str. faecalis cells and palygorskite under these conditions was studied by electron microscopy. It was established that there had been no bacte­rial interactions with the mineral particles at 10~4 mol/1 calcium chloride concen­tration in the dispersion medium. Particles of palygorskite not bound with bac­teria could be observed. But the rise of calcium chloride concentration to 10~3 mol/1 facilitates bacterial interaction with the mineral. Particles of paly­gorskite are sorbed on the bacterial cell surface, and a layer or "shell" of the mine­ral particles around a bacterium. In other words, bacterium-mineral complex: is formed. So, data of microelectrophoretic studies were proved by the results of elec­tron microscopic investigation of interaction between Str. faecalis cells and paly­gorskite in calcium chloride solutions. Microorganism-mineral complex with electrokinetic properties of the mineral particles is formed due to the increased interaction within the system. The same complex are brought about by the inte­raction of E . coli cells and montmorillonite in calcium chloride solutions. Interaction between E . coli cells and palygorskite in these solutions was also studied. Bacterial С-potential and that of the mineral pacticles were disco-132 L . Globa, A. Gordienko, V . Lesichkov, S. Garbara vered to be rather alike. Under such conditions we failed to detect the palygor-skite particles effect on electrokinetic properties of E . coli cells by microelectro­phoresis. Microelectrophoretic study of interaction between E .co l i cells and montmoril-lonite in aluminium chloride solutions showed that higher salt concentrations in dispersion medium caused lower or neutral negative surface charge, or even re­charge of bacteria and the mineral particles. E . coli cells in montmorillonite so­lutions have the value of С-potential, characteristic for the mineral particles at aluminium chloride concentration in dispersion medium two orders lower than that in calcium chloride solution (fig. 2). We have got similar results of the study of interaction between E . coli cells and montmorillonite in aluminium chloride solutions and the data on the hydro­gen ions effect upon the interaction in the system (6, 7). Bacterium — clay mi­neral complexes are formed at the negative values of С-potential of cells and the sorbent particles < 30 mV. But data on bacterial interaction with mineral sor-bents in calcium chloride solutions differ from the results achieved in dispersion media with the above mentioned cations. This interaction isn't pronounced even at the negative values of ^-potential of cells and mineral particles < 20 mV. Bacterium — clay mineral complexes are formed when calcium chloride con­centration is 10~3 mol/1 and content of palygorskite is < 20 mg/1. These data allow us to consider the given concentration of calcium chloride to be the condi­tion for an active interaction between bacteria and mineral sorbent. Microorganisms have greater aggregative and kinetic stability than mineral admixtures in water due to hydrophilic properties of their cells surface and elec­tric charge (14). Dispersion of E . coli and Str. faecalis cells may be regarded as a rather stable one. We transformed these bacteria into isoelectric state by decreas­ing their pH and polyvalent cations in the medium (12, 15), but all this hasn't resulted in the cell coagulation. Contrary to our results, but according to other authors (14), some microorganisms may aggregate while their negative C-poten-tial is decreased to 15 mV. We were able to destabilize microbe dispersions only in the presence of mine­ral sorbents. Microbe cell-mineral sorbent complexes are formed during intensive bacterial interaction with clay minerals. Surface properties of these comple­xes are characteristic for those of the mineral particles, and their aggregative stability is lower than that of microbe dispersion, which makes bacterial water purification by coagulation easier. Decrease of ^-potential of the montmorillo­nite particles to 10 mV is enough for the efficient mineral removal from water during coagulation in the volume. Therefore, microorganism-mineral sorbent complexes are necessary for the microbe dispersion destabilization. We have established that the formation of such complexes is not specific and that they are formed due to application of E . co­l i and Str. faecalis cells (12, 15), and palygorskite or montmorillonite, which all differ from each other by their composition, structure, physical and chemical properties (16). Composition of dispersion medium, concentration, and the type of cation in particular, has a strong effect on the efficiency of interaction between microor­ganisms and highly-dispersed minerals. Bacterial interaction with mineral sor­bents may be controlled by changing the dispersion medium composition. Since it is possible to obtain bacterium — mineral sorbent complexes, stable microbe dispersions may now be replaced by inorganic dispersions that are better removed from water by traditional coagulation technique (1 , 2). Effect of Ca 2 -f and A l 3 + ions on. 133 Thus we have investigated the mechanism of interaction between microorga­nisms and mineral sorbents in dispersion media with various ion compositions, and have improved our knowledge of the microbe dispersion destabilization and intensification of the bacterial coagulation removal from water by using such highly-dispersed mineral sorbents as montmorillonite and palygorskite. Natural resources of mineral sorbents are enormous and they find still wider application in water purification these days (16). Their ability to destabilize microbe dispersions in the presence of coagulating ions provides for further ad­vance of natural and waste water treatment. R E F E R E N C E S ] 1. Б а б е н к о в, Е. Д . Очистка воды коагулянтами. М., Наука , 1977. 356 с. — 2. К у л ь с к и й, Л . А. Теоретические основы и технология кондиционирования воды. Киев, Наукова думка, 1983. 528 с. — З. Л е с и ч к о в, В. С , Л . И. Г л о б а, Л . Г. К и р и л л о в а. — I n : Internat Congr. Infect. Parasit. Dis . , V I I . Varna, 2—6. X . 1978. Reports. V o l . 3, 5 5 5 — 5 5 8 . - 4. К а п p е л я н, Г., В. Л е с и ч е н к о, В. Р у с е в , Н. Е н ч е в . Сб. науч. тр. СНРБ — клон Варна, 1, 1977, № 1, 76—82. — 5. R u s е v , V . , V . E f t i m o v a , V . G a r d e v s k a , G . K a p r e l y a n , V . L e s i c h k o v , N . Е n с h е v. Scr. sci. Ted. 13, 1976, 118—120. — 6. Г л о б а, Л . И. , А. С. Г о р д и -е н к о, С . В . Г а р б а р а, М. Н. Р о т м и с т р о в , А. С. К у з е м а . Хим. и технол. воды, 1981, № 6, 549—551. — 7. Г л о б а, Л . И., А. С. Г о р д и е н к о, С В . Г а р -б а р а , М. Н. Р о т м и с т р о в . Микробиол. ж., 1983, № 2, 22—26. — 8. З в я г и н ­ц е в , Д . Г. Взаимодействие микроорганизмов с твердыми поверхностями. М., Изд. Москов­ского университета, 1973. 176 с. — 9. К о к и н а, А. Г., Н. А. Л у к а ш е в и ч , А. К. Д у ш к е в и ч , Н. В. Н о в и ц к а я . Гиг. и сан., 1978, № 7, 21—24. — 10. К о у -з о в , П. А. Основы анализа дисперсного состава промышленных пылей и измельченных материалов. Л . , Химия, 1974, 280 с. — 11. Г л о б а , Л . И., А. С Г о р д и е н к о. Мед. техн. (М.), 1980, № 2, 50—51. — 12. Г л о б а, Л . И., А. С. Г о р д и е н к о, М. Н. Р о т м и с т р о в . Хим. и технол. воды, 1981, № 5, 466—468. — 13. Б и р ю з о в а , В. И., В. Л . Б о р о в я г и н, В. П. Г и л е в, Н. А. К и с и л е в, А. С Т и х о -н е н к о , Ю . С. Ч е н ц о в . Электронно-микроскопические методы исследования биоло­гических обьектов. М., Издательство АН СССР, 1963. 204 с. — 14. Б ъ р д а р о в, С , К. М а р к о в . Микробиология. С , Медицина и физкултура, 1972. 508 с. — 15. Г о р -д и е н к о, А. С , Л. И. Г л о б а , М. Н. Р о т м и с т р о в . Докл. АН Укр. ССР, сер. Б , 1978, № 5, 426—428. — 16. Т а р а с е в и ч, Ю. И. Природные сорбенты в процессах очистки воды. Киев, Наукова думка, 1981. 208 с. ВЛИЯНИЕ ИОНОВ Са 2+ И А1 3 + НА ВЗАИМОДЕЙСТВИЕ БАКТЕРИЙ С МИНЕРАЛЬНЫМИ СОРБЕНТАМИ Л. Глоба. А. Гордиенко, В. Лесичков, С. Гарбара Р Е З Ю М Е Концентрация и тип катиона дисперсионной среды, а также содержание в ней глинис­того минерала монтмориллонита или палыгорскита существенно влияют на взаимодействие клеток Escherichia coli 163 и Streptococcus faecalis 134 с минеральными сорбентами. В опти­мальных условиях на поверхности микробной клетки коагулируют высокодисперсные ча­стицы минерала. Они образуют слой, окружающий бактерию в виде «оболочки». Такие ком­плексы бактерия — минеральный сорбент приобретают электрокинетические свойства, ха­рактерные для частиц минерала. По сравнению с бактериальными клетками, комплексы имеют пониженную агрегативную и кинетическую устойчивость. Выяснен механизм деста­билизации микробных дисперсий с помощью минеральных сорбентов, перспективы исполь­зования минералов и состава дисперсионной среды для повышения эффективности коагуля-ционной очистки воды от микроорганизмов. 

EFFECT OF CA2+ AND AL3+ IONS ON INTERACTION BETWEEN BACTERIA AND MINERAL SORBENTS

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EFFECT OF CA2+ AND AL3+ IONS ON INTERACTION BETWEEN BACTERIA AND MINERAL SORBENTS

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