Cheetah do not abandon hunts because they overheat

Hunting cheetah reportedly store metabolic heat during the chase and abandon chases because they overheat. Using biologging to remotely measure the body temperature (every minute) and locomotor activity (every 5 min) of four free-living cheetah, hunting spontaneously, we found that cheetah abandoned hunts, but not because they overheated. Body temperature averaged 38.4°C when the chase was terminated. Storage of metabolic heat did not compromise hunts. The increase in body temperature following a successful hunt was double that of an unsuccessful hunt (1.3°C ± 0.2°C versus 0.5°C ± 0.1°C), even though the level of activity during the hunts was similar. We propose that the increase in body temperature following a successful hunt is a stress hyperthermia, rather than an exercise-induced hyperthermia.     

Movement pattern of red deer during drive hunts in Sweden

We investigated the movement pattern of GPS-collared red deer (Cervus elaphus) during drive hunts with loose dogs. In 46 flights of hinds (N?=?9), the median flight distance was 2.5 km (range 0.4–15.0). In 28 % of the flights, the hind left its home range. Average time before returning to home range was 23 h (range 2–88). Hinds in a less forested site left their home ranges more often, fled longer distances, moved at higher speed, and returned later than hinds in a homogenous forest. Speed of movement increased with number of hunts in the less forested site. In eight flights of stags (N?=?4), the median flight distance was 5.1 km (range 2.2–13.3). The start of hunting season seemed to trigger stags’ departure to their wintering areas. Knowledge of reactions to disturbance can aid game management to choose hunting methods and dogs that cause less disturbance but may also be used to deter deer from areas where they damage crops and forest plantations.     

Single bacterial cell detection using a mutant luciferase

Previously, we constructed a genetically modified luciferase of Photinus pyralis that generates more than 10-fold higher luminescence intensity than the wild-type enzyme. In this study, we demonstrate that this modified luciferase enables us to detect ATP at 10⁻¹⁸ mol, which is almost equal to the quantity contained in a single bacterial cell. Consequently,we have been able to detect bacterial contamination in samples as low as one colony-forming unit (c.f.u.) for both Escherichia coli and Bacillus subtilis.     

Censusing rainforest game species with communal net hunts

This paper presents a method to address two wildlife management problems in central African rainforests: the need for local communities to take responsibility for wildlife management, and the lack of simple and appropriate wildlife monitoring techniques. The method uses encounters of game species during net hunts to calculate abundance indices as well as to estimate population densities for the four principal game species in the Dzanga–Sangha region: the duikers Cephalophus monticola (10.7–20.4 km^?2), C. dorsalis (1.2–2.0 km^?2), and C. callipygus (0.9–1.2 km^?2), and the brush-tailed porcupine Atherurus africanus (2.7–5.3 km^?2). Game species behaviour, the hunting practice, and comparisons with results from other research across central Africa suggest that the method can provide valid density estimates for C. monticola and C. dorsalis, but only abundance indices for C. callipygus and A. africanus. Nevertheless, the method can be applied by hunters in the course of their normal activities, and is adapted to the local habitat types and game species. As such, it can be an important tool for local communities in developing sustainable wildlife management programmes.     

Quinone reduction via secondary B-branch electron transfer in mutant bacterial reaction centers

Symmetry-related branches of electron-transfer cofactors-initiating with a primary electron donor (P) and terminating in quinone acceptors (Q)-are common features of photosynthetic reaction centers (RC). Experimental observations show activity of only one of them-the A branch-in wild-type bacterial RCs. In a mutant RC, we now demonstrate that electron transfer can occur along the entire, normally inactive B-branch pathway to reduce the terminal acceptor Q(B) on the time scale of nanoseconds. The transmembrane charge-separated state P(+)Q(B)(-) is created in this manner in a Rhodobacter capsulatus RC containing the F(L181)Y-Y(M208)F-L(M212)H-W(M250)V mutations (YFHV). The W(M250)V mutation quantitatively blocks binding of Q(A), thereby eliminating Q(B) reduction via the normal A-branch pathway. Full occupancy of the Q(B) site by the native UQ(10) is ensured (without the necessity of reconstitution by exogenous quinone) by purification of RCs with the mild detergent, Deriphat 160-C. The lifetime of P(+)Q(B)(-) in the YFHV mutant RC is >6 s (at pH 8.0, 298 K). This charge-separated state is not formed upon addition of competitive inhibitors of Q(B) binding (terbutryn or stigmatellin). Furthermore, this lifetime is much longer than the value of approximately 1-1.5 s found when P(+)Q(B)(-) is produced in the wild-type RC by A-side activity alone. Collectively, these results demonstrate that P(+)Q(B)(-) is formed solely by activity of the B-branch carriers in the YFHV RC. In comparison, P(+)Q(B)(-) can form by either the A or B branches in the YFH RC, as indicated by the biexponential lifetimes of approximately 1 and approximately 6-10 s. These findings suggest that P(+)Q(B)(-) states formed via the two branches are distinct and that P(+)Q(B)(-) formed by the B side does not decay via the normal (indirect) pathway that utilizes the A-side cofactors when present. These differences may report on structural and energetic factors that further distinguish the functional asymmetry of the two cofactor branches.     

Subunit exchange between and specific activities of mutant bacterial luciferases

Complementation has been demonstrated between two mutant bacterial luciferases which possess low activities due to different structural defects in different subunits. Activity characteristic of the wild type dimer was obtained by incubating under non-denaturing conditions. The specific activities of the two mutant enzymes were determined by using specific antiserum made against the wild type luciferase.     

Seeking clarity within cloudy effluents: differentiating fungal from bacterial peritonitis in peritoneal dialysis patients

Background

Fungal peritonitis is a serious complication of peritoneal dialysis (PD) therapy with the majority of patients ceasing PD permanently. The aims of this study were to identify risk factors and clinical associations that may discriminate between fungal from bacterial peritonitis.

Methods

We retrospectively identified episodes of fungal peritonitis from 2001–2010 in PD patients at Liverpool and Westmead Hospitals (Australia). Fungal peritonitis cases were matched in a 1∶2 ratio with patients with bacterial peritonitis from each institution''s dialysis registry, occurring closest in time to the fungal episode. Patient demographic, clinical and outcome data were obtained from the medical records.

Results

Thirty-nine episodes of fungal peritonitis (rate of 0.02 episodes per patient-year of dialysis) were matched with 78 episodes of bacterial peritonitis. Candida species were the commonest pathogens (35/39; 90% episodes) with Candida albicans (37%), Candida parapsilosis (32%) and Candida glabrata (13%) the most frequently isolated species. Compared to bacterial peritonitis, fungal peritonitis patients had received PD for significantly longer (1133 vs. 775 catheter-days; p = 0.016), were more likely to have had previous episodes of bacterial peritonitis (51% vs. 10%; p = 0.01), and to have received prior antibacterial therapy (51% vs. 10%; p = 0.01). Patients with fungal peritonitis were less likely to have fever and abdominal pain on presentation, but had higher rates of PD catheter removal (79% vs. 22%; p<0.005), and permanent transfer to haemodialysis (87% vs. 24%; p<0.005). Hospital length of stay was significantly longer in patients with fungal peritonitis (26.1 days vs. 12.6 days; p = 0.017), but the all-cause 30-day mortality rate was similar in both groups. Fluconazole was a suitable empiric antifungal agent; with no Candida resistance detected.

Conclusion

Prompt recognition of clinical risk factors, initiation of antifungal therapy and removal of PD catheters are key considerations in optimising outcomes.     

Selective perturbation of the second electron transfer step in mutant bacterial reaction centers

In order to specifically perturb the primary electron acceptor B(A) -- a monomeric bacteriochlorophyll (BChl) a -- involved in bacterial photosynthetic charge separation (CS), the protein environment of B(A) in the reaction center (RC) of Rhodobacter sphaeroides was modified by site-directed mutagenesis. Isolated RCs were characterized by redox titrations, low temperature optical spectroscopy, ENDOR/TRIPLE resonance spectroscopy and femtosecond time-resolved spectroscopy. Two mutations were studied: In the GS(M203) mutant a serine is introduced near the ring E keto group of B(A), while in FY(L146) a phenylalanine near the ring A acetyl group of B(A) is replaced by tyrosine. In all mutations the oxidation potential of the primary electron donor P as well as the electronic structure of both the P(*+) radical cation and the radical anion of the secondary electron acceptor, H(A)(*-), are not significantly altered compared to the wild type (WT), while changes of the optical absorption spectra at 77 K in the BChl Q(X) and Q(Y) regions are observed. The GS(M203) mutation only leads to a minor retardation of the CS reactions at room temperature, whereas for FY(L146) significant deviations from the native electron transfer (ET) rates could be detected: In addition to a faster first (2.9 ps) and a slower second (1 ps) ET step, a new 8-ps time constant was found in the FY(L146) mutant, which can be ascribed to a fraction of RCs with slowed down secondary ET. The results allow us to address the functional role of the acetyl group of B(A) and question the role of the free energy changes as the main determining factor of ET rates in RCs. It is concluded that structural rearrangements alter the electronic coupling between the pigments and thereby influence the rate of fast CS.     

Intestinal bacterial origin of D-alanine in urine of mutant mice lacking D-amino-acid oxidase.

Urine from mutant mice which lack D-amino-acid oxidase contained a large amount of D-alanine. The alanine content was not changed by changes in the dietary composition or by starvation. However, oral administration of an antibiotic, amoxicillin, decreased the urinary alanine to the normal level. These results suggest that the D-alanine is not of dietary origin but of intestinal bacterial origin.     

A lipopolysaccharide mutant of Bradyrhizobium japonicum that uncouples plant from bacterial differentiation.

The Tn5-containing fragment from a non-nodulating mutant of Bradyrhizobium japonicum, strain ML142, was introduced into B. japonicum strain 61A101c by marker exchange to construct strain JS314. Strain JS314 failed to nodulate several soybean varieties tested. However, on a few varieties nodulelike structures were induced to a frequency of 54% of the plants inoculated. The ultrastructure of these nodules was studied in detail by light and electron microscopy. The nodules were devoid of internal bacteria, possessed central vascular tissue (unlike the lateral vascular tissue of a normal nodule), and exhibited localized cell death of epidermal cells. Study of the cell surface polysaccharides of strain JS314 revealed that the exopolysaccharide of this strain was identical to that of the wild type. However, the lipopolysaccharide (LPS) of strain JS314 showed gross differences from that isolated from the wild-type strain. Specifically, the LPS of strain JS314 appeared to lack the high molecular weight LPS I form, strongly suggesting that the LPS lacks the O-chain. Glycosyl-composition analysis showed that the LPS of mutant JS314 lacked 2,3-di-O-methylrhamnose, 3-O-methylrhamnose, fucose, and quinovosamine. These results indicate that LPS I in B. japonicum is essential for bacterial infection of soybean, but is not required to initiate plant cortical cell division, an early plant response to infection.     

Similarities between a UV-sensitive mutant of yeast and bacterial mutants lacking excision-repair ability

Summary A UV-sensitive and a wild-type strain ofSaccharomyces cerevisiae have been compared with respect to their responses to photoreactivation, retention of the capacity to photoreactivate when stored at 32°C in buffer, and sensitivity to diepoxybutane and nitrosoguanidine. In all these tests the behaviour of the sensitive mutant paralleled bacterial strains lacking excision repair ability. We may tentatively attribute the UV sensitivity in this mutant to a loss of some element of a repair system analogous to excision repair in bacteria.