Characterization of the MCRred2 form of methyl-coenzyme M reductase: a pulse EPR and ENDOR study

Methyl-coenzyme M reductase (MCR), which catalyses the reduction of methyl-coenzyme M (CH(3)-S-CoM) with coenzyme B (H-S-CoB) to CH(4) and CoM-S-S-CoB, contains the nickel porphinoid F430 as prosthetic group. The active enzyme exhibits the Ni(I)-derived axial EPR signal MCR(red1) both in the absence and presence of the substrates. When the enzyme is competitively inhibited by coenzyme M (HS-CoM) the MCR(red1) signal is partially converted into the rhombic EPR signal MCR(red2). To obtain deeper insight into the geometric and electronic structure of the red2 form, pulse EPR and ENDOR spectroscopy at X- and Q-band microwave frequencies was used. Hyperfine interactions of the four pyrrole nitrogens were determined from ENDOR and HYSCORE data, which revealed two sets of nitrogens with hyperfine couplings differing by about a factor of two. In addition, ENDOR data enabled observation of two nearly isotropic (1)H hyperfine interactions. Both the nitrogen and proton data indicate that the substrate analogue coenzyme M is axially coordinated to Ni(I) in the MCR(red2) state.     

Potential for pre-release diet supplements to increase the sexual performance and longevity of male Queensland fruit flies

1 Recent studies have shown that continuous access to a protein source (yeast hydrolysate) can greatly enhance the sexual performance of male Queensland fruit flies ( Bactrocera tryoni ; 'Q-flies'). However, in Sterile Insect Technique programmes used to eradicate or suppress wild populations, mass-reared Q-flies are typically fed only sucrose and water for up to 2 days before release.
2 We investigated whether adding a protein source to the diet of male Q-flies for a 24- or 48-h window after emergence and then removing it is sufficient to enhance mating probability, latency to mate, copula duration, probability of sperm storage, number of sperm stored, female remating tendency and longevity of male Q-flies.
3 Protein-fed males were more likely to mate than males fed only sucrose, especially when young. Protein-fed males also had shorter mating latencies and longer copulations than protein-deprived males.
4 Females mated by protein-fed males were more likely to store sperm, stored more sperm and were less likely to remate than were females mated by protein-deprived males. Females were also less likely to remate if their first mate had been large.
5 Overall, providing male Q-flies access to a protein source for a 24- or 48-h window early on in their adult life was sufficient to greatly enhance all assessed measures of performance. Although 24-h access was sufficient for a notable enhancement, further benefits were evident in males provided 48-h access.
6 The results are discussed in terms of the practical implications for Sterile Insect Technique programs used to eradicate or suppress wild Q-fly populations.     

A direct observation of bacterial coverage and biofilm formation by Acidithiobacillus ferrooxidans on chalcopyrite and pyrite surfaces

To obtain a fundamental understanding of the population behaviour of Acidithiobacillus ferrooxidans at chalcopyrite and pyrite surfaces, the early stage attachment behaviour and biofilm formation by this bacterium on chalcopyrite (CuFeS₂) and pyrite (FeS₂) were studied by optical microscopy, Raman spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS) and electron backscatter diffraction (EBSD). The results indicate there was no significant difference in selectivity of bacterial attachment between chalcopyrite and pyrite. However, the result of ToF-SIMS analysis suggests that the surface of the pyrite was covered more extensively by biofilm than that of the chalcopyrite, which may indicate more extracellular polymeric substances (EPS) formation by bacterial cells growing on pyrite. EBSD and optical image analysis indicated that selectivity of bacterial attachment to chalcopyrite was not significantly affected by crystal orientation. The results also suggest that the bacterial population in defective areas of chalcopyrite was significantly higher than on the polished surfaces.