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PubMedDate not supplied

[Subordination of the taxa of gram-negative bacteria determined by numerical analysis methods].

Various numerical methods were used to estimate the coordination of taxa of gram-negative aerobic and facultative anaerobic organoheterotrophic and chemolithotrophic bacteria. Stable phena were found to be formed by cultures belonging to the families Rhizobiaceae, Halobacteriaceae, Enterobacteriaceae, Nitrobacteriaceae (except the genus Nitrobacter), and Methylomonadaceae (except the genus Methylococcus). The unstable position was found in the genera Thermus, Zoogloea, Xanthomonas, Sulfolobus, Methylococcus, Alcaligenes, Brucella, and Acetobacter. The greatest scatter among the objects being analysed was detected among genera belonging to the family Pseudomonadaceae. The taxonomic position of these genera must be defined more precisely. The family Methylomonadaceae is related to such physiologically unique groups of microorganisms as nitrifying, sulfate-reducing, extreme thermophilic and halophilic forms. All in all, the data reported in this work show that numerical analysis can be used to specify the classification structure of bacteria. In a number of cases, the results are consistent with those changes which are performed in the Bergey Manual 9 using logical analysis (for instance, concerning the position of the genera Gluconobacter, Acetobacter, Beijerinckia, and Derxia).

Bacteriological Techniques↗
PubMedDate not supplied

[The endotoxins of gram-negative bacteria: their structure and biological role].

Main attention in the paper is paid to the study of lipid A, a component possessing endotoxic activity. Lipids A containing glucosamine disaccharide (representatives of Enterobacteriaceae family), and variants of lipid A differing from the toxic one either in the structure of carbohydrate core or in the spectrum of fatty acids are considered. They are either phototrophic, nodulating (Bradyrhyzobium species) or soil species (Nitrobacter and Thiobacillus) bacteria. Lipid A from lipopolysaccharides of over 25 species of bacteria (Rhodopseudomonas viridans, R. palustris, Pseudomonas diminuta, Phenylobacterium immobile, Brucella melitensis, B. abortus, Thiobacillus ferrooxidans, etc.) contains 2.3-diamino-2.3-dideoxyglucose (lipid ADAG); glucosaminouronic acid was found in Rhizobium trifolii and galacturonic acid in R. leguminosarum bvs. phaseoli, trifolii and viceae. Mixed lipids (lipid A and lipid ADAG) were found in Campylobacter jejuni. Considerable variations were registered in the nature of fatty acids. Thus, 27-oxy-octacosanoic acid (27-OH-28 : 0) was found in lipid A of the studied species of Rhizobiaceae except for Azorhizobium caulinodans. No correlations between the composition of the carbohydrate core and presence of this acid were established. Implementation of the synthesis of a complete as well as of partial lipid A structures has confirmed authenticity of the described structures. Five different epitopes identified by antibodies are present in the hydrophilic part of lipid A. The structure and biological role of the outer and inner cores are considered separately, main attention being paid to identification of the role of the KDO-containing zone. Since O-specific polysaccharide is the most known lipopolysaccharide component from the viewpoint of the structure and biological activity, this material is given in a general form.

Endotoxins↗
PubMed2006

Development and calibration of a nitrification PDE model based on experimental data issued from biofilter treating drinking water.

To remove ammonia for production of drinking water, nitrification can be performed in a bio-filter. At least 1 month is necessary to capture from the groundwater and then grow a sufficient amount of nitrifying bacteria to reach the desired removal efficiency. Improving start-up of bio-filters at low substrate concentration is therefore a major challenge. In this connection, it is important to develop appropriate models for designing, monitoring or analysing biofilm systems during start-up or following disinfection events. This study discusses the development and calibration of a nitrification PDE model which reflects the compromise between the complexity associated with the description of the full physical and biochemical mechanisms and the search for a simplified model with identifiable parameters. This model takes only the relevant phenomena (considering the full operating range) into account. The validity of the calibrated model has been evaluated through experiments under very different operational conditions, at the laboratory and under real industrial conditions, involving the full upstream chain of water treatment (iron oxidation and sand filter).

Ammonia↗