Filamentous Population Research Articles

Response of pioneer soil microalgal colonists to environmental change in Antarctica

There is increasing evidence of climate change in Antarctica, especially elevated temperature and ultraviolet B (UVB) flux within the ozone "hole." Its origins are debatable, but the effects on ice recession, water availability, and summer growth conditions are demonstrable. Light-dependent, temperature-sensitive, fast-growing organisms respond to these physical and biogeographical changes. Microalgae (cyanobacteria and eukaryotic algae), which are pioneer colonists of Antarctic mineral fellfield soils, are therefore highly suitable biological indicators of such changes. In frost-heaved soil polygons containing naturally sorted fine mineral particles, microalgal growth is restricted to a shallow zone of light penetration. By virtue of this light requirement, microalgae are exposed to extreme seasonal fluctuations in temperature (air and black-body radiation), photosynthetically active radiation, UV radiation, and desiccation. Dominance of conspicuous autofluorescent indicator species with distinctive morphology allowed quantification of responses using epifluorescence microscopy, and image analysis of undisturbed, unstained communities. However, the physical changes in climate, although significant in the long term, are gradual. The changes were therefore amplified experimentally by enclosing the communities at a fellfield site on Signy Island, maritime Antarctica, in cloches (small greenhouses). These were made of polystyrene of either UV transparent or UV opaque acrylic plastic, with or without walls. During a 6-year period, statistically significant changes were observed in microalgal colonization of the soil surface and in the morphology of filamentous populations. Evidence of community succession correlated with measured changes in local environment was found. Results from Signy Island and at continental sites on Alexander Island suggested that rates of microalgal colonization and community development might change significantly during current climate changes in Antarctica.

Development of the microbial community of a full scale biological nutrient removal activated sludge plant during start-up

The bacterial populations capable of accumulating polyphosphate in pure culture were followed during the first 10 months of operation of a full scale biological nutrient removal plant with a modified U.C.T. configuration. Special emphasis was placed on the Acinetobacter isolates obtained. Results showed that of these, most could be identified as A. johnsonii (genospecies 7) although other genospecies including 9 and 12 were also found in smaller numbers. A large number of these could not be identified with the Biology system. Several other Gram positive and Gram negative bacterial genera capable of removing polyphosphate were also isolated from the biomass. The filamentous bacterial populations seen in the mixed liquor and foam were monitored regularly over this period, and after early changes, Microthrix parvicella and Eikelboom Types 0092 and 0041/0675 gradually assumed dominance in the mixed liquor, while Nocardia amarae-like organisms and Type 0092 together with M. parvicella were in the foam.

A simple descriptive model of filamentous fungi spore germination

A simple statistical model is presented to describe the germination kinetics of filamentous fungal spore populations grown either in soluble or on solid substrates. The model attempts to reduce large amounts of data to three parameters of relevant physiological significance: one related to the maximum proportion of germination in a spore population, another related to the kinetics of the process, and another — the synchronization factor — that measures the extent of synchronization in the population of germinating spores. The latter is a very important parameter, which is introduced for the first time in a model of spore germination, and which, together with the other two, would be considered in relation to filamentous fungal fermentations in physiological and technological studies. These parameters were estimated by the Maximum Likelihood method. The fit of our experimental data, together with associated data reported in the literature indicated the validity of the model for the description of the time course of germination for a large variety of strains grown under different physical and chemical environmental conditions.

Middle to Late Proterozoic microbiota from the Deoban Limestone, Garhwal Himalaya, India

A well-preserved Middle to Late Proterozoic microbial assemblage from the Deoban Limestone (Formation), Chakrata region, Garhwal Himalaya, is described from petrographic thin sections of black bedded chert. The present assemblage contains both filamentous and coccoid forms which are mostly of cyanobacterial affinity. The assemblage includes 28 species belonging to sixteen genera and two forms of uncertain affinity described as unnamed forms A and B. Eoentophysalis, Glenobotrydion and Myxococcoides are the three most abundant coccoid forms constituting about 40% of the total coccoid population. The diameter of coccoids ranges between 1.5 and 65 μm. Gunflintia, Biocatenoides and Eomycetopsis are the three dominating filementous genera constituting about 90% of the filamentous population. The width of the filaments ranges between 0.5 and 18 μm. The diversity in coccoids is greater in comparison with filamentous forms. The total assemblage comprises: Coccoid forms— Myxococcoides minor, M. inornata, Eosynechococcus isolatus, Glenobotrydion aenigmatis, G. majorinum, Melasmatosphaera media, M. parva, Tetraphycus major, T. conjunctum, Globophycus rugosum, Huroniospora psilata, H. microreticulata, Caryosphaeroides pristina, Eoentophysalis magna, E. belcherensis, E. cumulus, Gloeodiniopsis gregaria, G. lamellosa, G. sp., Sphaerophycus parvum, unnamed form A and unnamed form B. Filamentous forms— Gunflintia grandis, G. minuta, Biocatenoides sp., Eomycetopsis robusta, E. filiformis, E. siberiensis, Siphonophycus kestron and Oscillatoriopsis sp. The assemblage shows an abundance of small coccoids and thin filaments as compared to larger coccoids and thicker filaments. The abundance of forms decreases with the increase in diameter in coccoid forms and width in filamentous forms.

Design criteria for population selection in activated sludge

The competition between floc-forming and non-settling filamentous populations has been analysed for an activated sludge process incorporating a plug-fl

A survey of filamentous bacterial populations from foaming activated sludge plants in Eastern States of Australia

Of 129 activated sludge plants surveyed during 1988 in Queensland, New South Wales and Victoria, 66 had a foam problem during the sampling period. Filament identification revealed that Microthrix parvicella, Nocardia amarae and Nocardia pinensis were the most commonly found, followed by Eikelboom types 0092, 0914 and 0041/0675, although their relative frequencies varied from state to state.

Response of Microorganisms to Hot Crude Oil Spills on a Subarctic Taiga Soil

This study was conducted on the short-term effects of seasonal spills of hot Prudhoe Bay crude oil on microorganisms in a taiga soil in interior Alaska. Following a winter spill, the filamentous fungal populations were inhibited whereas the heterotrophic bacterial populations were stimulated. After a summer spill there was an initial depression of both the filamentous fungal and bacterial populations followed by a general enhancement. In both oil spill plots, yeasts; along with the denitrifying, proteolytic, oil-utilizing, and cellulose-utilizing microorganisms; were favorably affected by the oil. Soil respiration was also enhanced in the oiled plots. An extended period of study is required to fully evaluate the impact of oil on the soil microflora and the role of these microorganisms in recovery of oil-inundated areas in subarctic ecosystems.

Bacterial growth rates and temperature optima in a stream with a fluctuating thermal regime1

Direct measurement of bacterial growth rates in a natural stream showed that the unicellular and filamentous populations had doubling times of 42–51 hr when the water temperature was 0–5°C, 8.4–10.8 hr when water temperature was predominantly 11–16°C, and 2.8–6.0 hr when the water temperature was 16.5–21.0°C. The populations were not optimally adapted to the prevailing stream water temperature, but rather to temperatures 5–20°C higher.

Turnover of murein in cellular and filamentous populations of Bacillus megaterium.

Bacillus megaterium grows in the form of filaments at temperatures above 45°C. The rate of turnover of the cell wall begins to decrease gradually under these conditions. At the same time sensitivity of the filamentous forms to lysozyme decreases. Filaments outgrown at 48°C retain the decreased rate of turnover of the cell wall for a certain time after transfer to 30°C, in spite of the fact that septa are formed and filaments are converted to cells. However, a population incubated longer than 2 h at 48°C often ceases to grow and the growth is not restored even after transfer to 30°C. Three clones of the asporogenic strainBacillus megaterium KM differing somewhat in their ability to form filaments at 35°C differ mutually also in the rate of turnover of the cell wall. However, the decreased rate of the turnover cannot be unambiguously correlated with the increased tendency to form filaments.

Studies of two kinds of virus particles which comprise influenza A2 virus strains. III. Morphological characteristics: independence to morphological and functional traits.

Seven strains of influenza A2 virus were serially passed in the chick embryo, and morphological characteristics of the passages were examined in the electron microscope. With serial passage there was a change from a prominently filamentous appearance in early passages to an almost entirely spherical appearance in later passages. The number of passages required for the conversion to spherical morphology varied with different strains. The filament-sphere variation was found to be independent of the properties which differentiate "+" and "-" influenza A2 virus particles, and both highly filamentous and spherical populations of "+" and of "-" virus particles were obtained. The usefulness of these pairs of independent markers for genetic studies is discussed.