Photosynthetic characteristics of coccoid marine cyanobacteria

Two strains of marine Synechococcus possessed a much greater potential for photorespiration than other marine algae we have studied. This conclusion was based on the following physiological and biochemical characteristics: a) a light-dependent O₂ inhibition of photosynthetic CO₂ assimilation at atmospheric O₂ concentrations. The degree of inhibition was dependent on the relative concentrations of dissolved O₂ and CO₂, being greatest at 100% O₂ with no extra bicarbonate added to the medium; b) actively photosynthesizing cells had high levels of ribulose-1,5-bisphosphate carboxylase compared with phosphoenolpyruvate carboxylase; ribulose-1,5-bisphosphate oxygenase activities were three times greater than ribulose-1,5-bisphosphate carboxylase activities; c) cells photosynthesizing in 21% O₂, showed significant ¹⁴C-labelling of phosphoglycolate and glycolate and the percentage of total carbon-14 incorporated into these two compounds increased when the O₂ concentration was 100%; d) at 100% O₂, there was a post-illumination enhanced rate of O₂ consumption, which was three times greater than dark respiration, and the rate declined with increasing bicarbonate concentrations. The inhibitory effect of O₂ on photosynthesis did not appear to be solely due to photorespiration, since O₂ inhibition of photosynthetic O₂ evolution was much greater than that of photosynthetic CO₂ assimilation. Also, O₂ inhibition of photosynthetic O₂ evolution declined only slightly with decreasing light intensities, while the inhibition of CO₂ assimilation declined rapidly with decreasing light intensity.     

Production and viability of coccoid forms of Campylobacter jejuni

Studies were conducted into the formation and physiological state of coccoid cells of a strain of the human and animal pathogen Campylobacter jejuni. It was found that growth phase and the presence of chloramphenicol did not affect the rate of shape transformation from spiral to coccoid, while nutrient limitation, aeration of the medium and the presence of free-radical scavengers had profound effects. Coccoid cells were found to reduce the tetrazolium salts INT (2-( p -iodophenyl)-3-( p -nitrophenyl)-5-phenyl tetrazolium chloride) and CTC (5-cyano-2,3-ditolyl tetrazolium chloride) to their respective formazans and this was linked to cellular respiration. However, respiring coccoid cells could not sustain their existence in prolonged adverse conditions, and it was concluded that they represent a degenerative stage rather than a dormant state of the organism.     

Helicobacter pylori– coccoid forms and biofilm formation

Electron microscopic studies have shown that Helicobacter pylori occurs in three stages: spiral forms, coccoid forms and degenerative forms. The spiral forms are viable, culturable, virulent and can colonize experimental animals and induce inflammation. The coccoid forms may also be viable but are nonculturable, less virulent and are less likely to colonize and induce inflammation in experimental animals than the spiral forms. The degenerative forms are pyknotic, nonculturable, coccoid forms of dead H. pylori . These forms cannot be cultured and the cell membrane has disintegrated but gene material can be detected by PCR in water supplies. There is no substantial evidence for viable H. pylori persisting in water supplies. Epidemiological studies suggest that environmental water is a risk factor for H. pylori infection when compared with tap water, and formation of H. pylori biofilm cannot be excluded. Helicobacter pylori does not seem to take part in biofilm formation in the oral cavity even though the bacterium may be detected.     

Detection of coccoid forms of Sulfitobacter mediterraneus using atomic force microscopy

The adhesion of the marine alpha-Proteobacteria Sulfitobacter pontiacus, Sulfitobacter mediterraneus, Sulfitobacter brevis, and Staleya guttiformis to a poly(tert-butyl methacrylate) (PtBMA) polymeric surface generates unusual cell morphological peculiarities following attachment. While the type strains S. pontiacus and S. brevis failed to attach to PtBMA, the vegetative cells of type strain S. mediterraneus underwent morphological conversion into coccoid forms during the attachment over an incubation period of 24-72 h. Type strain St. guttiformis cells formed a multilayered biofilm on the PtBMA surface, presumably facilitated by bacterial production of extracellular polysaccharides. The attachment behavior and fine structure of these coccoid forms have been described using atomic force microscopy. The impact of polymeric surfaces of defined hydrophobicity on the formation of coccoid bodies is discussed.     

A comparative study of the rod and coccoid forms of Campylobacter jejuni ATCC 29428

Coccoid forms in cultures of a strain of the enteric pathogen Campylobacter jejuni were investigated. A culture containing 100% coccoid forms was non-viable. Coccoid forms had a lesser content of cytoplasmic components and nucleic acids than rods of C. jejuni. During the conversion to coccoid forms nucleotides leaked from the cells. The results of treatments with ionic and non-ionic detergents, and lysozyme and ethylenediaminetetraacetic acid indicated a changed cell wall in coccoid forms compared with rods. Using rate-zonal centrifugation coccoid forms were found to be less dense than rods. The results of this study indicate that the coccoid form of C. jejuni ATCC 29428 is a degenerate cell form which is undergoing cellular degradation.     

Spectral characteristics of Micropolyspora spp. and of actinomycetes similar to them]

IR spectra of the whole cells of oligosporous actinomycetes were studied. These spectra can be used as an additional criterion during identification of actinomycetes at the generic level, and confirm the heterogeneity of the Micropolyspora genus so that some of its species may be classed as an individual genus (Kalakoutskii et al., 1968; Agre, Dorokhova, 1972).     

A comparative study of the rod and coccoid forms of Campylobacter jejuni ATCC 29428

Coccoid forms in cultures of a strain of the enteric pathogen Campylobacter jejuni were investigated. A culture containing 100% coccoid forms was non-viable. Coccoid forms had a lesser content of cytoplasmic components and nucleic acids than rods of C. jejuni. During the conversion to coccoid forms nucleotides leaked from the cells. The results of treatments with ionic and non-ionic detergents, and lysozyme and ethylenediaminetetraacetic acid indicated a changed cell wall in coccoid forms compared with rods. Using rate-zonal centrifugation coccoid forms were found to be less dense than rods. The results of this study indicate that the coccoid form of C. jejuni ATCC 29428 is a degenerate cell form which is undergoing cellular degradation.     

Role of antibiotics in the ecology of actinomycetes]

The organisms producing ristomycin, rifamycin, lincomycin, tobramycin, rubomycin carminomycin, olivomycin, bleomycin and actinomycin D were practically not sensitive to their own antibiotics in the concentrations close to those produced during the biosynthetic process. At the same time other actinomycetous species close to the above organisms were suppressed to a significant extent by their antibiotics in the same concentrations. The experimental data indicated that the antibiotics had a protective effect on the organisms producing them and played a significant role in ecology of the actinomycetes.     

Oxadin effect on actinomycetes strains]

The results of research show that oxadin has mutagenous effect on the tested actinomyces strains, in particular on Streptomyces albus--producer of the polyether antibiotic salinomycin. The colonies grown up after spores treatment with oxadin, have been tested for auxotrophy, morphological mutations and biosynthesis of the antibiotic salinomycin. Treatment of Streptomyces albus strain with 10% oxadin for 10 or 20 min provided the isolation of highly active strains. Dispersion analysis data revealed statistically significant differences between the control (non treated) and the oxadin-treated Streptomyces albus populations.     

Factors affecting production of coccoid forms by Campylobacter jejuni on solid media during incubation

Conditions influencing the conversion of oxygen into toxic derivatives in media were investigated for their effects on production of coccoid forms in cultures of the enteric pathogen Campylobacter jejuni. Compared with stored media, production of coccoid forms was less on freshly prepared media. Whether freshly prepared or stored before use, brucella agar media produced the fewest coccoid forms under the test conditions. Addition of supplements used as detoxifying agents minimized production of these forms on media but antibiotic formulations used in selective media did not influence production of coccoid forms. Furthermore, the type of incubation atmosphere and the strain of C. jejuni influenced the proportions of coccoid forms in cultures. It was deduced from electron microscopy observations during prolonged incubation of cultures that the process of conversion to coccoid forms involves a loss of spiral morphology, a shortening of the cell and retraction of the cytoplasm towards a cell terminal region. Coccoid forms and some intermediate forms in thin sections were found to lack cell integrity. It is concluded that coccoid form production in cultures is a degenerate response to toxic oxygen derivatives in cultures.     

Immunodiffusion and fluorescent antibody methods to distinguish rod from coccoid forms of a species ofArthrobacter

Immunological methods for distinguishing rod from coccus forms of anArthrobacter species are presented. Diffusion precipitation tests indicate that the rod form is antigenically more complex than the coccus form with respect to both soluble and cell-wall fractions. Antisera prepared against fractions of coccus and rod forms are able, after cross absorption, to specifically label rod and coccus forms.     

Spectrophotometric study of the system DNA-lipid]

The effect of some physical and chemical factors on the system DNA-lipid and its components was studied by spectrophotometry. A change of optical density (D) of watersalt suspensions of lipid total fraction in the range of wavelengths from 200 to 350 nm with the change of ionic strength from 0 to 1 M NaC1 and temperature from 20 to 100 degrees C was investigated. Measurements were carried out under various temperature regemes. In all cases a bell-like irreversible dependence of D on temperature was observed. Its parameters were essentially dependent on the temperature heating of the samples and medium composition. In the presence of DNA the parameters of the curve were changed significantly and depended on the ratio DNA:lipid. An inhibiting effect of DNA on the oxidation of lipids and stabilization of liposomes as well as thermic destruction of DNA stabilized by lipids were observed under certain conditions. The data obtained allowed a conclusion concerning the formation of lipodesoxinucleic complex. It was shown that when a large number of lipid oxidation products was accumulated in the system a chemical modification of DNA with the change of its secondary structure went on.     

Micronuclei in mucose cells and colonization of human stomach epithelium with coccoid forms of Helicobacter pylori

International Agency for Research on Cancer recognized as sufficient the evidence of Helicobacter pylori (HP) infection carcinogenicity and placed it into the 1 st group of carcinogens. Micronucleus level in gastric epithelial cells of antral stomach region of patients with chronic non-atrophy gastritis (n = 62) was studied. 40 patients of 62 had HP-associated gastritis. The HP-bacterium exists in a spiral and coccoid form. Both morphological forms were examined using immunocytochemistry. Significantly increased micronucleus number was observed in the cells of HP-infected patients compared with non-infected person (P < 0.05). The frequency of stomach epithelium cells with micronuclei was enhanced considerably in the patients infected with the coccoid HP form. Therefore the patients with HP-associated chronic gastritis caused by the coccoid form with high degree of colonization must be considered as a group of enhanced risk of gastric carcinogenesis.     

The comparative characteristics of different forms of allergens from mites of the genus Dermatophagoides]

The comparative study of allergenic preparations of Dermatophagoides mites [correction of ticks] from different manufacturers and the international standard preparations of such allergens was made. D. pteronyssinus and D. farinae allergens from the USSR and the Netherlands were studied. The samples under study were evaluated in a complex of in vivo and in vitro experiments. The preparations produced in the USSR and in the Netherlands exhibited pronounced specificity, but the allergens of both species from the Netherlands were more active. Some differences in the immunochemical characteristics of the preparations were noted.     

Effect of medium supplements, illumination and superoxide dismutase on the production of coccoid forms of Campylobacter jejuni ATCC 29428

Factors influencing the production of coccoid forms in cultures and suspensions of a strain of the enteric pathogen Campylobacter jejuni during storage in air were investigated. Addition of blood or a supplement containing ferrous sulphate, sodium metabisulphite and sodium pyruvate minimized conversion of rods to coccoid forms in cultures. Exposure of cultures to light during storage in air increased the rate of production of coccoid forms. Ultraviolet radiation was shown to effect the viability of cells in suspensions but the increase in production of coccoid forms was low after irradiation. The presence of hydrogen peroxide and its dissociation products in bacterial suspensions increased conversion to coccoid forms. Addition of active superoxide dismutase, a superoxide anion scavenging enzyme, minimized production of coccoid forms in suspensions stored in air. Coccoid forms contained a lower level of superoxide dismutase than rods. It is deduced that a decreased level of the enzyme in cells is linked with production of coccoid forms.