Inter-species sequence conservation of single-spanning transmembrane regions

The extent of inter-species sequence identity in single-spanning transmembrane regions of integral membrane proteins was evaluated. The sequences of the 32 human transmembrane regions were compared with the respective rodent homologues. The identity between homologous transmembrane regions ranged from 32 to 100%, compared with a mean value of 14% identity between unrelated transmembrane sections. On average the identity between homologous transmembrane regions is slightly higher than for the rest of the chain. These values suggest that, in general, there are structural and/or functional constraints on the transmembrane regions beyond the simple requirement to act as a passive, nonpolar, connecting region across the cell membrane. Although there is limited experimental evidence available, the three transmembrane regions (CD2 antigen, MHC class I and ICAM-1) with particularly low values of inter-species identity (less than 50%) are probably not involved in an interaction with another transmembrane section in the same cell.     

Information-related changes in contact patterns may trigger oscillations in the endemic prevalence of infectious diseases

It is well known that behavioral changes in contact patterns may significantly affect the spread of an epidemic outbreak. Here we focus on simple endemic models for recurrent epidemics, by modelling the social contact rate as a function of the available information on the present and the past disease prevalence. We show that social behavior change alone may trigger sustained oscillations. This indicates that human behavior might be a critical explaining factor of oscillations in time-series of endemic diseases. Finally, we briefly show how the inclusion of seasonal variations in contacts may imply chaos.     

Catastrophic floods may pave the way for increased genetic diversity in endemic artesian spring snail populations

The role of disturbance in the promotion of biological heterogeneity is widely recognised and occurs at a variety of ecological and evolutionary scales. However, within species, the impact of disturbances that decimate populations are neither predicted nor known to result in conditions that promote genetic diversity. Directly examining the population genetic consequences of catastrophic disturbances however, is rarely possible, as it requires both longitudinal genetic data sets and serendipitous timing. Our long-term study of the endemic aquatic invertebrates of the artesian spring ecosystem of arid central Australia has presented such an opportunity. Here we show a catastrophic flood event, which caused a near total population crash in an aquatic snail species (Fonscochlea accepta) endemic to this ecosystem, may have led to enhanced levels of within species genetic diversity. Analyses of individuals sampled and genotyped from the same springs sampled both pre (1988-1990) and post (1995, 2002-2006) a devastating flood event in 1992, revealed significantly higher allelic richness, reduced temporal population structuring and greater effective population sizes in nearly all post flood populations. Our results suggest that the response of individual species to disturbance and severe population bottlenecks is likely to be highly idiosyncratic and may depend on both their ecology (whether they are resilient or resistant to disturbance) and the stability of the environmental conditions (i.e. frequency and intensity of disturbances) in which they have evolved.     

Molecular epidemiology of group B streptococcal infections

Streptococcus agalactiae (GBS) is a causative agent of sepsis and meningitis in newborns and diseases in pregnant women and nonpregnant adults. Various approaches, including both nongenetic and genetic techniques, are currently used for the study of epidemiology of GBS infections. In the present paper the different methods of molecular epidemiology of GBS infections are reviewed, and several novel approaches are introduced. The advantages and disadvantages of molecular methods are discussed and compared with traditional serotyping technique. The possible use of the molecular approaches for identification of different genetic lineages in GBS as well as for identification and control of the epidemiologically actual clones is discussed.     

Uncovering the mysteries of invasive streptococcal diseases

Group A streptococci, although considered extracellular pathogens, are capable of causing severe life-threatening invasive infections, such as necrotising fasciitis, bacteraemia and toxic-shock-like syndrome. A complete understanding of the mechanism by which these organisms cause invasive disease has been hampered by the extreme human specificity and high genetic diversity among group A streptococci. Three recent papers have uncovered some of the mysteries of streptococcal invasive diseases. Using two different technologies, these papers have contributed enormously towards our understanding of the molecular events underlying streptococcal invasive diseases.     

Comparative analysis of mitochondrial genome data for Necator americanus from two endemic regions reveals substantial genetic variation

Necator americanus is a blood-sucking, intestinal nematode of major human health importance in many tropical and subtropical regions of the world. The aim of the present study was to compare the complete mitochondrial genome sequence from one N. americanus individual from Togo with another from China, in order to estimate the magnitude of genetic variability for different mitochondrial genes and non-coding regions. For the 12 protein genes, this comparison revealed sequence differences at both the nucleotide (3-7%) and amino acid (1-7%) levels. The most conserved of these was the nad4L gene, whereas the nad1 gene was least conserved at both the nucleotide and amino acid levels. Nucleotide differences were also detected in 14 of the 22 transfer RNAs (trns) (1-13%), the AT-rich region ( approximately 8%), non-coding regions (8-25%) and in the small (rrnS) and large (rrnL) subunits of mitochondrial ribosomal RNA (rrn) ( approximately 1%). Comparison of the rrnL sequences among multiple individual worms revealed nine unequivocal nucleotide differences between N. americanus from the two countries. Consistent with previous studies, these findings provide evidence for substantial genetic variation within N. americanus, which may have implications for the transmission and control of hookworm disease.     

A random process may control the number of endemic species

The richness of endemic species is often recognized as an indication of the distinctiveness of certain local faunas and is used for the definition of conservation hotspots as well. Faunas of different animal taxa were considered in sets of contiguous geographical units. Comparing the faunas of different units in one set, we found an exponential increase in the number of endemics when plotted against the number of non-endemics. A model of independent stochastic population dynamics under the control of environmental oscillations produces random fluctuations in the ranges of species. Ranges of endemic species are supposedly narrower than ranges of co-occurring non-endemic species. In such a case, the flow of a random process leads to an exponential relationship between numbers of co-occurring endemic and non-endemic species. This process also produces an apparent positive correlation between total species number and the percentage of endemics.     

Molecular epidemiology of infectious diseases

Data on molecular epidemiology of bacterial infections is summarized. The term definitions of "molecular epidemiology", "taxonomic species" are given, the limits and species structure of prokaryotes are described. The basic mechanisms of the prokaryotes variability in the epidemic process, as well as the possibilities and limitations of microbiological, molecular-biological and population--genetic typing methods, are characterized. The tactics of molecular-biological studies in analyzing the population structure on the global, regional and local levels is presented. The economic effectiveness of measures taken with due consideration of information on the clonal structure of causative agents of hospital infections is shown.     

Detection of anthrax spores in endemic regions of northern Canada

AIMS: To determine the level of anthrax spore contamination in endemic regions of northern Canada between outbreaks. METHODS AND RESULTS: Bacterial endospores were extracted from specimens via flotation and cultured on selective PLET medium. Of 588 environmental specimens collected, 11 (1.9%) contained viable anthrax spores. CONCLUSION: High environmental concentrations of anthrax spores in northern Canada appear limited to scavenger faeces and anthrax carcass sites. Burial and cremation appear equally effective at removing anthrax spores from the immediate environment, though cremation may be improved by re-burning cremation sites containing unburned animal hair. SIGNIFICANCE AND IMPACT OF THE STUDY: This study describes an effective anthrax spore detection system. It provides the first bacteriological evidence that mammalian scavengers can disseminate anthrax spores in northern Canada, and its results may be compared with future environmental studies of untreated anthrax carcass sites to help improve government response plans.     

A role for the fibrinogen-binding regions of streptococcal M proteins in phagocytosis resistance

All virulent group A streptococcal isolates bind fibrinogen, a property that is closely linked to expression of type-specific antiphagocytic surface molecules designated M proteins. Here we show that although the M proteins from two different strains, M1 and M5, both bind fibrinogen with high affinity, they interact with different regions in the ligand. Moreover, mapping experiments demonstrated that the fibrinogen-binding regions in the M1 and M5 proteins are quite dissimilar at the amino acid sequence level and that they bind to different regions in the plasma protein. In spite of these differences, the fibrinogen-binding regions of M1 and M5 could both be shown to contribute to streptococcal survival in human blood, providing evidence for the distinct function of a plasma protein interaction in bacterial pathogenesis.