Isolation of Physarum amoebal mutants defective in flagellation and associated morphogenetic processes (original) (raw)
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Journal of bacteriology, 1973
When cells of Proteus vulgaris were transferred from 37 to 42 C, a temperature at which they continue to grow almost optimally, they ceased to form flagella after approximately one generation time. This failure was due to a lesion in the flagellin-synthesizing process rather than the inability of these cells to assemble the organelle from constituents once formed. After transfer back to 37 C, these cells regained their ability to synthesize flagellin and form flagella, after one generation. When added during this period, chloramphenicol, rifampin, or penicillin prevented the synthesis of flagellin. The regeneration of the organelle at 37 C, then, requires growth for one generation, a period during which not only ribonucleic acid and protein synthesis, but also the presence of an intact cell envelope or concurrent synthesis of cell wall, are required.
Journal of Invertebrate Pathology, 1974
Naegleria gruberi amoebae, EGs strain, containing viruslike particles (VLP) were grown at temperatures of 21" and 37°C. At 21"C, the amoebae displayed the morphological structures associated with development of the VLP's. At 37"C, however, gross morphological modifications and new structures appeared. When amoebae were at 37°C for less than 12 hr, nuclei were found to have a larger number of VLP's than amoebae at 21°C. Exposure of the amoebae to the higher temperature for 1224 hr resulted in. a scarcity of particles. Large bundles of microtubulelike fibrils were present in the nucleoplasm of amoebae at 37"C, and, in addition, the nuclei showed degenerative modifications. The fibrillar changes were not due to the elevated temperature alone since a substrain of EGs ( = EGB) not infected with VLP's exhibited no nuclear modifications. It is assumed that the elevated temperature acaeleratrd upon the cells. and enhanced a lytic effect of the VLP's 172
Use of cell cultures as an indicator of pathogenicity of free-living amoebae
Journal of Clinical Pathology, 1978
Results comparing the time needed for the development of cytopathic effects in cell cultures with that needed to cause death in mice using inocula of Naegleria and Acanthamoeba are presented. The significance of the source and concentration of the inocula is demonstrated. The use of cell cultures as an indicator of the pathogenicity of free-living amoebae is discussed. Material and methods AMOEBAE N. fowleri strain HB-1, Naegleria gruberi strain Ng 1518, and Acanthamoeba culbertsoni strain A-I were supplied by the Culture Centre for Algae and Protozoa, Cambridge, UK. N. fowleri strains NTH, PA14, NHI, and MsT and N. gruberi strains Ng-27 and PL200f were obtained from Dr R. A. Robinson of the National Health Institute, Wellington, New Zealand. N. gruberi strains BH and BL were obtained from Ms N. Davies, of
Morphological response of cultured cells to Naegleria amoeba cytopathogenic material
Journal of Cell Science, 1985
Naegleria amoebae contain cytopathogenic material (NACM). The morphological response of cultured cells to this material follows a number of characteristics in common with those resulting from infectious agents. The cytopathologic changes varied depending on the strain of the cultured cells. Among those from 17 different vertebrate sources, both primary and continuous cell lines, some were destroyed completely by dilutions of NACM up to 10~8 while others appeared unaffected by NACM at any concentration. The response had no apparent relationship to species, organ source, or passage level of the cells. The reaction was typified by a long latent period (4-10 days) during which the number of cells in the culture increased up to 10-fold, followed abruptly by a short period (less than 24 h) during which all of the cells were destroyed. The latent period was prolonged when the culture conditions were adverse, or when the amount of NACM in the inoculum was minimal. A high multiplicity of NACM in the inoculum lysed the entire culture, while dilutions near the endpoint caused generalized or only focal changes of rounded cytopathic cells. The cytopathic effect could be maintained in cultured cells by serial passage, such that the total activity greatly exceeded what could be attributed to the original inoculum. These findings are consistent with the concept that NACM has properties of an infectious agent and that its quantity is enhanced and spread through the culture by cell-to-cell contact and by cell division.
FEMS Microbiology Letters, 2016
Legionella pneumophila is a pathogenic bacterium commonly found in water and responsible for severe pneumonia. Free-living amoebae are protozoa also found in water, which feed on bacteria by phagocytosis. Under favorable conditions, some L. pneumophila are able to resist phagocytic digestion and even multiply within amoebae. However, it is not clear whether L. pneumophila could infect at a same rate a large range of amoebae or if there is some selectivity towards specific amoebal genera or strains. Also, most studies have been performed using collection strains and not with freshly isolated strains. In our study, we assess the permissiveness of freshly isolated environmental strains of amoebae, belonging to three common genera (i.e. Acanthamoeba, Naegleria and Vermamoeba), for growth of L. pneumophila at three different temperatures. Our results indicated that all the tested strains of amoebae were permissive to L. pneumophila Lens and that there was no significant difference between the strains. Intracellular proliferation was more efficient at a temperature of 40 • C. In conclusion, our work suggests that, under favorable conditions, virulent strains of L. pneumophila could equally infect a large number of isolates of common freshwater amoeba genera.
Transformation of straight flagella and recovery of motility in a mutant Escherichia coli
Journal of Molecular Biology, 1978
The non-motjilc strain W3623 ha-177 of Escherichia coli (Kondoh & Ozeki, 1976) is known to produce straight flagella as a result of a mutation in the structural gene for the flagellin. Under physiological conditions, however, flagella of this mutant undergo straight-to-helical transformation with small changes of pH. Evidence for this came from dark-field light microscope observations of reconstituted flagella. At pH values lower than 6.6 in the presence of 0.1 M-NaCl, the flagella were straight. When, however, the pH was raised above 7.3, they were transformed into left-handed helices with a pitch of 2.05 pm. The transformation was rapid and reversible. In the pH range between 6.6 and 7.3, straight and transformed flagella co-existed but no stable forms ot,her than the two were found. Bacterial motility also depended on the pH of the medium: at pH values above 7.0, bacteria swam by means of the transformed flagella. Therefore, helically transformed flagella of the mutant strain were similar in morphology and function to normal-type flagella of the parent strain. The significance of this similarity is discussed on the basis of general considerations of polymorphism in bacterial flagella.
Protistology, 2019
Nucleophaga amoebae belongs to the phylum Rozellomycota (Opisthokonta), a widespread clade of parasites, considered as intermediate link between fungi and microsporidia. This organism is an obligate intranuclear parasite of the free-living amoeba Thecamoeba quadrilineata. The life cycle of this organism is difficult to study, many details require further clarification, and available light-microscopic images are limited in number and quality. We performed real-time observations on the process of parasite propagation in amoeba culture using Eppendorf Cell Imaging Plates and Differential Interference Contrast (DIC) microscopy. Development of the parasite was traced from the engulfment of spores by the amoeba cell to the production of a new generation of spores. Nucleophaga cells proliferate inside the host nucleus. The earliest intranuclear developmental stages that we observed were rounded uninucleate cells located at the margin of the host nucleolus. Growth resulted in formation of a large multinucleate plasmodium, which further became segregated into numerous individual uninucleate sporoblasts. After a period of maturation, sporoblasts transformed into the rounded spores enclosed in the sporophorous vesicle, probably formed by the remnants of the membrane of the plasmodium. At the final stage of the developmental cycle the amoeba cell died, its envelope, as well as the nuclear membrane broke, and the spores were released into the environment. The developmental cycle took approximately 5 days. Infected amoebae never divided, so we can suggest that the infection suppressed mitosis in the host cell.
The sheathed flagellum of Pseudomonas stizolobii
Journal of general microbiology, 1969
Organisms of two strains of Pseudomonas stizolobii possessed one polar flagellum of unusual thickness. Negative-contrast staining and ultrathin sectioning indicated that the flagella are sheathed and are comparable in structure to the sheathed flagella described in Vibrio and Bdellovibrio. In some instances, flagella displayed sheath and core structure after negative constrast staining. Distal 'tubules ' and ' knobs ' apparently consisting entirely of sheath material were also seen. The thickness of the sheath, which in section consisted of an outer dense component and an inner lighter component, was similar to that of the outer double track membrane of the cell wall. I N T R O D U C T I O N During the examination of a collection of species of Pseudomonas for the presence of fimbria-like appendages (Fuerst & Hayward, 1969), unusual polar flagella were seen on Pseudomonas stizolobii (Wolf) Stapp, 1935. This species is a plant pathogen causing a disease of the leaves and stems of mainly leguminous plants (Burkholder, 1957; Rothwell & Hayward, 1964). Whereas flagella of most bacteria are 120 to 150 A in diameter and, under the electron microscope at high resolution, preparations of negatively stained material exhibit a helical aggregate of globular subunits, (Joys, 1968 ; Doetsch & Hageage, 1968), the flagella of P. stizolobii were of greater thickness and lacked the substructure characteristic of unsheathed bacterial flagella. Our aim was to determine by electron microscopic techniques the nature of the flagellum of P. stizolobii and to compare it with the sheathed flagella which are known to occur in a very few genera of Gram-positive and Gram-negative bacteria. METHODS Organisms and media. Pseudomonas stizolobii NCPPB 450 and P. stizolobii strain 0268 A, as listed by Fuerst & Hayward (1969), were grown at 28O in either motility medium (Difco bacto peptone, 5.0 g. ; glycerol, 5.0 g. ; MgS04. 7H20, 0.25 g. ; K2HP04, 0.5 g.; Difco agar, 3.0 g.; distilled water, I l.), peptone yeast extract broth (see Fuerst & Hayward, 1969), or glucose peptone yeast extract broth (glucose, I g.; peptone yeast extract broth, IOO ml.).
Flagella and Motility in Actinobacillus pleuropneumoniae
Journal of Bacteriology, 2003
Actinobacillus pleuropneumoniae has been considered nonmotile and nonflagellate. In this work, it is demonstrated that A. pleuropneumoniae produces flagella composed of a 65-kDa protein with an N-terminal amino acid sequence that shows 100% identity with those of Escherichia coli, Salmonella, and Shigella flagellins. The DNA sequence obtained through PCR of the fliC gene in A. pleuropneumoniae showed considerable identity (93%) in its 5 and 3 ends with the DNA sequences of corresponding genes in E. coli, Salmonella enterica, and Shigella spp. The motility of A. pleuropneumoniae was observed in tryptic soy or brain heart infusion soft agar media, and it is influenced by temperature. Flagella and motility may be involved in the survival and pathogenesis of A. pleuropneumoniae in pigs.
Temperature-sensitive mutants of the slime mould Physarum polycephalum
Molecular and General Genetics, 1976
Methods are described for the isolation and testing of temperature-sensitive plasmodial strains of Physarum polycephalum. Nineteen temperature-sensitive strains were found by screening plasmodia derived from mutagenised amoebae and the properties of these are described. A scheme is outlined for the detection of specific mitotic cycle lesions amongst temperature-sensitive strains, and the properties of a presumptive mitotic cycle mutant are described.