Injury and recovery in freeze- or heat-damaged Campylobacter jejuni

When exposed to freezing or heat, cells of Campylobacter jejuni were initially sensitized to rifampicin and, with longer exposures, subsequently unable to grow on nutrient or blood agar. Repair of all lesions occurred within 2 h at 37°C while at 43°C organisms were only able to repair the presumably less severe injury caused by short exposures to high or low temperature.     

On the 13C/12C isotopic signal of day and night respiration at the mesocosm level

While there is currently intense effort to examine the ¹³C signal of CO₂ evolved in the dark, less is known on the isotope composition of day‐respired CO₂. This lack of knowledge stems from technical difficulties to measure the pure respiratory isotopic signal: day respiration is mixed up with photorespiration, and there is no obvious way to separate photosynthetic fractionation (pure c_i/c_a effect) from respiratory effect (production of CO₂ with a different δ¹³C value from that of net‐fixed CO₂) at the ecosystem level. Here, we took advantage of new simple equations, and applied them to sunflower canopies grown under low and high [CO₂]. We show that whole mesocosm‐respired CO₂ is slightly ¹³C depleted in the light at the mesocosm level (by 0.2–0.8‰), while it is slightly ¹³C enriched in darkness (by 1.5–3.2‰). The turnover of the respiratory carbon pool after labelling appears similar in the light and in the dark, and accordingly, a hierarchical clustering analysis shows a close correlation between the ¹³C abundance in day‐ and night‐evolved CO₂. We conclude that the carbon source for respiration is similar in the dark and in the light, but the metabolic pathways associated with CO₂ production may change, thereby explaining the different ¹²C/¹³C respiratory fractionations in the light and in the dark.     

Genetic portrait of Lisboa immigrant population from Cabo Verde with mitochondrial DNA analysis

Journal of Genetics -     

Tropical acid streams – the chironomid (Diptera) response in northern Australia

1. Chironomidae, sampled by interception of drifting cast pupal exuviae, responded to inputs of acid, heavy metal-rich waters in a seasonally flowing tropical stream in northern Australia.
2. Responses included gain of distinctive (indicative) taxa, loss of some species typical of pristine conditions, and increase in species richness.
3. Experimental manipulation (upstream diversion) of a mine adit entry showed that these responses were the result of change in water quality.
4. The higher species richness at low pH, which is contrary to temperate studies, may be explained by the large tropical (Australian and south-east Asian) pool of species tolerant of naturally occurring acidic aquatic habitats.
5. The structure and responses of the exuvial-assessed chironomid community matched long-term larval data.