Evidence of an endogenous circannual rhythm in growth-rates in dinoflagellates

Prorocentrum micans and Gonyaulax excavata clonal cultures grown under constant laboratory environmental conditions (continuous light and 20 +/- 1 degree C), over a two-year period, exhibit significative changes in growth rate. When rhythmometrically analyzed by cosinor, a pattern resembling a circannual rhythm became apparent. Significant rhythmometric differences appeared between species. Endogenous rhythms of microorganisms may have ecological implications.     

Identification of ''Campylobacter upsaliensis'' and other catalase-negative campylobacters from paediatric blood cultures by numerical analysis of electrophoretic protein patterns

Twenty-one strains of catalase-negative campylobacters from paediatric blood cultures were characterized by one-dimensional SDS-PAGE of cellular proteins. A further 11 Campylobacter strains were included for reference purposes. The partial protein patterns were used as the basis of a numerical analysis, which showed that 17 hippurate-negative strains had a high similarity to 'C. upsaliensis' (r greater than or equal to 0.82) irrespective of their geographical location, and that three hippurate-positive isolates had a high similarity (r greater than or equal to 0.87) to C. jejuni subsp. jejuni. One hippurate-positive CNW strain was not identified. The analysis of SDS-PAGE protein patterns proved an excellent method of characterizing these thermophilic campylobacter as they were difficult to identify by traditional methods.     

Elucidation of trophic interactions in an unusual single-cell nitrogen-fixing symbiosis using metabolic modeling

Marine nitrogen-fixing microorganisms are an important source of fixed nitrogen in oceanic ecosystems. The colonial cyanobacterium Trichodesmium and diatom symbionts were thought to be the primary contributors to oceanic N₂ fixation until the discovery of the unusual uncultivated symbiotic cyanobacterium UCYN-A (Candidatus Atelocyanobacterium thalassa). UCYN-A has atypical metabolic characteristics lacking the oxygen-evolving photosystem II, the tricarboxylic acid cycle, the carbon-fixation enzyme RuBisCo and de novo biosynthetic pathways for a number of amino acids and nucleotides. Therefore, it is obligately symbiotic with its single-celled haptophyte algal host. UCYN-A receives fixed carbon from its host and returns fixed nitrogen, but further insights into this symbiosis are precluded by both UCYN-A and its host being uncultured. In order to investigate how this syntrophy is coordinated, we reconstructed bottom-up genome-scale metabolic models of UCYN-A and its algal partner to explore possible trophic scenarios, focusing on nitrogen fixation and biomass synthesis. Since both partners are uncultivated and only the genome sequence of UCYN-A is available, we used the phylogenetically related Chrysochromulina tobin as a proxy for the host. Through the use of flux balance analysis (FBA), we determined the minimal set of metabolites and biochemical functions that must be shared between the two organisms to ensure viability and growth. We quantitatively investigated the metabolic characteristics that facilitate daytime N₂ fixation in UCYN-A and possible oxygen-scavenging mechanisms needed to create an anaerobic environment to allow nitrogenase to function. This is the first application of an FBA framework to examine the tight metabolic coupling between uncultivated microbes in marine symbiotic communities and provides a roadmap for future efforts focusing on such specialized systems.     

Numerical analysis of electrophoretic protein patterns of Providencia alcalifaciens strains from human faeces and veterinary specimens

Twenty-five strains of Providencia alcalifaciens from various countries have been characterized by one-dimensional SDS-PAGE of cellular proteins. They comprised 15 from human faeces, one from duck faeces, one from a guinea-pig eye and eight from unknown sources. Also included, for reference purposes, were the type strains of three other Providencia species. The protein patterns, which contained 45–50 discrete bands, were highly reproducible and were used as the basis for two numerical analyses. In the first, in which the principal protein bands (in the 33–40 kD range) were excluded, the 25 Prov. alcalifaciens strains formed, at the 83% S level, a single cluster whilst the three Providencia reference strains remained unclustered. In the second, which included all the protein bands, the 25 Prov. alcalifaciens strains formed 10 clusters at the 85% S level. We conclude that high resolution PAGE combined with computerized analysis of protein patterns provides the basis for typing clinical strains of Prov, alcalifaciens . Reference strains of each of the 10 PAGE types identified are available from NCTC for inclusion in future studies.     

Numerical analysis of electrophoretic protein patterns of Group EF-4 bacteria, predominantly from dog-bite wounds of humans

Thirty-seven strains of Group EF-4 bacteria (from various countries) were characterized by one-dimensional SDS-PAGE of cellular proteins. They comprised 21 from dog-bite wounds of humans, three from cat-bite wounds of humans and five from human limb wounds which may have been inflicted by dogs or cats; there was also one each from a pet monkey, a tiger lung (fatal), a dog tonsil, a mouse, a cat liver, a wallaby mandible, a human vagina and one from a human limb wound which was apparently not inflicted by an animal. The protein patterns, which contained 45 to 50 discrete bands, were highly reproducible and were used as the basis for three numerical analyses. In the first, in which the principal protein bands (in the 34.8 to 41.3 kD range) were excluded, the 37 Group EF-4 strains formed, at the 62% S level, two major clusters corresponding to strains producing a dihydrolase for arginine and those not doing so. In the second analysis, which included all the protein bands and which was performed only on the 22 arginine-positive strains, two phenons formed (one of which could be further divided into two sub-phenons) at the 56% S level. The third analysis, also based on all the protein bands, divided the 15 arginine-negative strains into three clusters at the 56% S level. We conclude that high resolution PAGE combined with computerised analysis of protein patterns correlates exactly with the separation of Group EF-4 into two biovars (also with the distinction of the biovars on the basis of G+C content). Reference strains of each of the PAGE types identified are available from the NCTC for inclusion in future studies.     

The influence of the slowing of Earth's rotation: A hypothesis to explain cell division synchrony under different day duration in earlier and later evolved unicellular algae

Every year the Earth's rotation period is reduced, mainly due to the tidal drag of the moon. The length of day increases continuously by about 1 h every 200 million years. The period of rotation around the Sun remains constant; hence, the length of the year remains constant, so years acquire progressively fewer days. Many unicellular algae show rhythmicity in their cell division cycle. If primitive algae evolved under a shorter day duration, then it is possible that the early-evolved algae had to synchronize their cell division cycle to shorter lengths of day than did later-evolved algae. We tested this hypothesis by growing Cyanobacteria, Dinophyceae, Prasinophyceae, Bacillariophyceae and Conjugatophyceae (evolutionary appearance probably in this order) at 8∶8 h light-dark cycles (LD), 10∶10 LD, and 12∶12 LD, at 20 or 27°C. Cyanobacteria synchronized their cell division cycles optimally at 8∶8 h LD, Dinophyceae and Prasinophyceae at 10∶10 h LD, and Conjugatophyceae and Bacillariophyceae at 12∶12 h LD. The synchrony of cell division was scarcely affected by temperature. Results suggested that the early evolved unicellular autotrophic organisms such as the Cyanobacteria synchronized their cell division cycle under a shorter day duration than later-evolved unicellular algae, and these traits may have been conserved by quiescent genes up to the present day.