When microbial conversations get physical

It is widely accepted that microorganisms are social beings. Whereas communication via chemical signals (e.g. quorum sensing) has been the focus of most investigations, the use of physical signals for microbial cell-cell communication has received only limited attention. In this Opinion article, I postulate that physical modes of microbial communication could be widespread in nature. This is based on experimental evidence on the microbial emission and response to three physical signals: sound waves, electromagnetic radiation and electric currents. These signals propagate rapidly, and even at very low intensities, they provide useful mechanisms when a rapid response is required. I also make some suggestions for promising future research avenues that could provide novel and unsuspected insights into the physical nature of microbial signaling networks.     

DNA repair gets physical: mapping an XPA-binding site on ERCC1

Two recent reports provide new physical information on how the XPA protein recruits the ERCC1-XPF heterodimer to the site of damage during the process of mammalian nucleotide excision repair (NER). Using chemical shift perturbation NMR experiments, the contact sites between a central fragment of ERCC1 and an XPA fragment have been mapped. While both studies agree with regard to the XPA-binding site, they differ on whether the ERCC1-XPA complex can simultaneously bind DNA. These studies have important implications for both the molecular process and the design of potential inhibitors of NER.     

When it gets cold,plant size matters – a comment on treeline

Many questions in vegetation science related to species ranges and species performance could be resolved by appropriate bioclimatological data. In the case of small‐stature plants, such as herbs and grasses, but also seedlings of trees, weather station data are inappropriate to describe their life conditions – an important point not only in empirical research, but also for modellers.     

When melatonin gets on your nerves: its beneficial actions in experimental models of stroke

This article summarizes the evidence that endogenously produced and exogenously administered melatonin reduces the degree of tissue damage and limits the biobehavioral deficits associated with experimental models of ischemia/reperfusion injury in the brain (i.e., stroke). Melatonin's efficacy in curtailing neural damage under conditions of transitory interruption of the blood supply to the brain has been documented in models of both focal and global ischemia. In these studies many indices have been shown to be improved as a consequence of melatonin treatment. For example, when given at the time of ischemia or reperfusion onset, melatonin reduces neurophysiological deficits, infarct volume, the degree of neural edema, lipid peroxidation, protein carbonyls, DNA damage, neuron and glial loss, and death of the animals. Melatonin's protective actions against these adverse changes are believed to stem from its direct free radical scavenging and indirect antioxidant activities, possibly from its ability to limit free radical generation at the mitochondrial level and because of yet-undefined functions. Considering its high efficacy in overcoming much of the damage associated with ischemia/reperfusion injury, not only in the brain but in other organs as well, its use in clinical trials for the purpose of improving stroke outcome should be seriously considered.     

The physical nature of life.

Life evolved from the primeval world of physics. Sensory systems inform animals of the natural environment, enabling them to conduct responsively. The discovery of weak, DC bioelectric fields in the vicinity of aquatic organisms and the role they play in guiding sharks and rays to their prey have led to the recognition of fundamental, hitherto less well known, physical aspects of sensory biology. The inferred cybernetic algorithm of electric-field orientation in sharks and rays is highly effective and extremely robust. In orienting to the weak DC electric fields of ocean currents and to the earth's magnetic field, sharks and rays unwittingly practise the motional-electric principles that Einstein had in mind when he introduced the special theory of relativity. At the sense-organ, receptor-membrane, and ion-channel levels, the elasmobranch ampullae of Lorenzini operate on the basis of graded positive feedback driven by negative conductance, supposedly employing voltage-sensitive ion channels as the active, excitable elements. The electric sense of sharks and rays presents an exquisite implementation of the very biophysical principles that also govern the graded, much richer than all-or-none, integrative brain processes of animal and man.     

When the going gets tough: survival strategies and environmental signaling networks in Bacillus subtilis.

Regulatory pathways involving two-component histidine kinase/response regulator proteins of Bacillus subtilis are highly interconnected and form a signal transduction network controlling stationary-phase adaptive responses. These include chemotaxis and motility, degradative enzyme synthesis, antibiotic production, natural competence for DNA uptake, and sporulation. Many of these responses are mutually exclusive, with different control levels involving protein-environment, protein-protein and protein-DNA interactions, allowing the bacteria to adapt rapidly to environmental changes.     

Quality of life in people with physical disabilities

The aim of this study was to examine the possible differences in self-reported quality of life of people with physical disabilities with regard to both socio-demographic and disability-related characteristics. Testing was conducted on 153 respondents with physical disabilities, residents of the City of Zagreb. Positive correlations were found between the quality of life and income satisfaction, residence size (per capita floor area) and level of residence equipment. Multivariate analysis of variance showed statistically significant differences in quality of life among respondents with regard to the marital status, work status and home ownership. Statistically significant differences in the quality of life were found among the participants depending on their level of physical mobility and type of physical disability. The level of physical mobility is associated with general satisfaction with the accomplishment of goals, aspirations and hopes. The type of physical disability is related to the satisfaction with leisure activities, with the material status, expectations to achieve in the future what has not formerly been achieved. There was also a significant relation between the type of physical disability and general satisfaction with life in the past year. Positive correlations between duration of disability and quality of life were found. Membership in associations of persons with physical disability and related benefits were shown to contribute to the quality of life.     

When the going gets tough: behavioural type-dependent space use in the sleepy lizard changes as the season dries

Understanding space use remains a major challenge for animal ecology, with implications for species interactions, disease spread, and conservation. Behavioural type (BT) may shape the space use of individuals within animal populations. Bolder or more aggressive individuals tend to be more exploratory and disperse further. Yet, to date we have limited knowledge on how space use other than dispersal depends on BT. To address this question we studied BT-dependent space-use patterns of sleepy lizards (Tiliqua rugosa) in southern Australia. We combined high-resolution global positioning system (GPS) tracking of 72 free-ranging lizards with repeated behavioural assays, and with a survey of the spatial distributions of their food and refuge resources. Bayesian generalized linear mixed models (GLMM) showed that lizards responded to the spatial distribution of resources at the neighbourhood scale and to the intensity of space use by other conspecifics (showing apparent conspecific avoidance). BT (especially aggressiveness) affected space use by lizards and their response to ecological and social factors, in a seasonally dependent manner. Many of these effects and interactions were stronger later in the season when food became scarce and environmental conditions got tougher. For example, refuge and food availability became more important later in the season and unaggressive lizards were more responsive to these predictors. These findings highlight a commonly overlooked source of heterogeneity in animal space use and improve our mechanistic understanding of processes leading to behaviourally driven disease dynamics and social structure.