Abstract
Here we describe the study of the sorption of high-molecular components of dissolved organic matter (DOM) of natural waters - humic acids - by eight bacterial strains isolated from freshwater. Isotherms of DOM sorption by cells are described by the Langmuir equation. Gram-positive bacteria adsorb more DOM than gram-negative bacteria, with high molecular weight DOM fractions binding in a relatively selective manner. A high positive correlation (r = 0.91) was found between the decrease in the molecular weight of DOM during the sorption of these compounds by cells and the maximum sorption value. The formation of a polysaccharide capsule increases the binding of DOM by the cells of Pseudomonas sp. to the level of gram-positive bacteria.
Highlights
Dissolved organic matter (DOM) is a mixture of individual low molecular weight compounds, fulvic acids and humic acids (HAs), the latter being the most high molecular weight components of this system [1]
The value of maximum sorption (Qmax) of DOM by bacterial cells lacking polysaccharide capsules ranged from 419 mg DOM/g dry biomass for gram-negative bacteria to 21-162 mg DOM/g dry biomass for gram-positive bacteria (Fig. 3, Table 1)
The appearance of a polysaccharide film on the cell wall surface leads to a decrease in the strength of DOM binding by the cells of Pseudomonas sp., in parallel with an increase in sorption; according to this parameter, the DOM sorption by a gramnegative bacterium approaches the sorption by a gram-positive cell of Paenibacillus sp. that is covered with a polysaccharide capsule (k = 7)
Summary
Dissolved organic matter (DOM) is a mixture of individual low molecular weight compounds, fulvic acids and humic acids (HAs), the latter being the most high molecular weight components of this system [1]. Bacteria are believed to consume mainly the low molecular weight labile DOM compounds, whereas the larger and more stable DOM compounds may play the role of biochemical regulators [4, 5, 6]. The transfer of dissolved organic matter from the solution to the surface of the cells of microorganisms does not qualitatively change the situation, but only localizes these processes near the cell membranes [7]. The study of the sorption of DOM components on the microbiome isolated from freshwater reservoirs has shown the predominant sorption of high molecular weight fractions of DOM [11]. The aim of this work was to study DOM sorption by bacterial cells and DOM fractionation by bacteria with different cell surface structures
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