The HemQ coprohaem decarboxylase generates reactive oxygen species: implications for the evolution of classical haem biosynthesis

Bacteria require a haem biosynthetic pathway for the assembly of a variety of protein complexes including cytochromes, peroxidases, globins, and catalase. Haem is synthesised via a series of tetrapyrrole intermediates including non-metallated porphyrins such as protoporphyrin IX, which is well-known to generate reactive oxygen species (ROS) in the presence of light and oxygen. Staphylococcus aureus has an ancient haem biosynthetic pathway that proceeds via the formation of coproporphyrin III, a less reactive porphyrin. Herein, we demonstrate for the first time that HemY of S. aureus is able to generate both protoporphyrin IX and coproporphyrin III, and that the terminal enzyme of this pathway, HemQ, can stimulate the generation of protoporphyrin IX (but not coproporphyrin III). Assays with hydrogen peroxide, horseradish peroxidase, superoxide dismutase, and catalase confirm that this stimulatory effect is mediated by superoxide. Structural modelling reveals that HemQ enzymes do not possess the structural attributes that are common to peroxidases that form compound I [FeIV=O]+, which taken together with the superoxide data leaves Fenton chemistry as a likely route for the superoxide-mediated stimulation of protoporphyrinogen IX oxidase activity of HemY. This generation of toxic free radicals could explain why HemQ enzymes have not been identified in organisms that synthesise haem via the classical protoporphyrin IX pathway. This work has implications for the divergent evolution of haem biosynthesis in ancestral microorganisms and provides new structural and mechanistic insights into a recently discovered oxidative decarboxylase reaction

High-bandwidth generation of duobinary and alternate-mark-inversion modulation formats using SOA-based signal processing

We report on the novel all-optical generation of duobinary (DB) and alternate-mark-inversion (AMI) modulation formats at 42.6 Gb/s from an input on-off keyed signal. The modulation converter consists of two semiconductor optical amplifier (SOA)-based Mach-Zehnder interferometer gates. A detailed SOA model numerically confirms the operational principles and experimental data shows successful AMI and DB conversion at 42.6 Gb/s. We also predict that the operational bandwidth can be extended beyond 40 Gb/s by utilizing a new pattern-effect suppression scheme, and demonstrate dramatic reductions in patterning up to 160 Gb/s. We show an increasing trade-off between pattern-effect reduction and mean output power with increasing bitrate

All-optical modulation converter for on-off keying to duobinary and alternate-mark inversion at 42.6 Gbps

Advanced modulation formats have become increasingly important as telecoms engineers strive for improved tolerance to both linear and nonlinear fibre-based transmission impairments. Two important modulation schemes are Duobinary (DB) and Alternate-mark inversion (AMI) [1] where transmission enhancement results from auxiliary phase modulation. As advanced modulation formats displace Return-to-zero On-Off Keying (RZ-OOK), inter-modulation converters will become increasingly important. If the modulation conversion can be performed at high bitrates with a small number of operations per bit, then all-optical techniques may offer lower energy consumption compared to optical-electronic-optical approaches. In this paper we experimentally demonstrate an all-optical system incorporating a pair of hybrid-integrated semiconductor optical amplifier (SOA)-based Mach-Zehnder interferometer (MZI) gates which translate RZ-OOK to RZ-DB or RZ-AMI at 42.6 Gbps. This scheme includes a wavelength conversion to arbitrary output wavelength and has potential for high-level photonic integration, scalability to higher bitrates, and should exhibit regenerative properties [2]

Effect of Temperature and Wind on Metabolism of Northern Bobwhite in Winter

Northern bobwhite (Colinus virginianus) are widely distributed across more than half of the United States, and extending into Canada and Mexico. Within this distribution they tolerate a wide range of climatic conditions and thermal stress. Annual variation in weather can produce dramatic short-term population fluctuations, particularly in the northern portion of the distribution. To better understand effects of thermal stress on energy requirements of bobwhite, we measured roosting metabolic response to cold stress and wind speed using open respirometry in a closed-circuit wind tunnel. Oxygen consumption was measured for 8 winter-acclimated captive bobwhites at each of 8 temperatures (-15°, -10°, -5°, 0°, 5°, 10°, 20°, and 30° C) at free convection and at 3 wind speeds (0, 1, and 2 m/sec) at -15° and 0° C. Over the range of body mass we measured (201.5 ± 1.3 g, n = 64), metabolic rate varied with body mass (P \u3c 0.001) but did not differ between sexes (P = 0.187). Mean standard metabolic rate (V02) was 3.4 ± 0.11 mL O2/minute/bird (0.0171 ± 0.0004 mL O2/ min/g) or 1.14 ± 0.04 W/bird. Below a lower critical temperature of 24.1° C, metabolic rate was linearly related to operative temperature (Te)(V02 = 7.187 - 0.1568[Te]; r2 = 0.86, P \u3c 0.001). Metabolic rate (M–E) was linearly related to wind speed (WS) at -15° C (V02 = 9.741 + 0.4609[WS]; r2 = 0.99, P = 0.001) and 0° C (V02 = 6.713 + 0.4609[WS]; r2 = 0.99, P = 0.001). We discuss implications of these energy expenditures in the context of current research and management

Relative Invertebrate Abundance and Biomass in Conservation Reserve Program Plantings in Northern Missouri

We measured relative invertebrate abundance, biomass, and diversity in Conservation Reserve Program (CRP) fields planted to red clover (Trifolium pratense)/timothy (Phleum pratense), timothy, orchard-grass (Dactylis glomerata), tall fescue (Festuca pratensis), warm-season grasses (big bluestem [Andropogon gerardi]/switch grass [Panicum virgatum]), orchard-grass/Korean lespedeza (Kummerowia stipu/,acea), and conventionally-tilled soybeans, to assess brood habitat quality for northern bobwhite (Colinus virginkinus). We sampled invertebrate populations by vacuuming along 3 15-m transects (4.56 m2/sample) within 4 fields of each planting type, at 2-week intervals from 1 July to 15 August 1990 and 1991. Invertebrate abundance and biomass were lowest in early August (P \u3c 0.05). The CRP fields planted to a red clover/timothy mixture, and dominated by red clover, had the highest levels of invertebrate abundance and biomass (P \u3c 0.05). Conventionally-tilled soybeans had lower invertebrate abundance and biomass than all CRP covertypes (P\u3c 0.05). Mean invertebrate abundance and biomass in CRP fields were 4 times that of soybean fields. In northern Missouri, CRP fields could provide quality brood habitat if structural characteristics are also consistent with brood foraging needs. Incorporation of a legume in CRP plantings may produce higher invertebrate densities and improve the value of these fields as brood habitat

Redescription of Serpinema octorugatum (Baylis, 1933) (Nematoda:Camallanidae) from the Malayan box turtle Cuora amboinensis (Daudin)(Chelonia: Bataguridae)

We redescribe the camallanid nematode Serpinema octorugatum (Baylis, 1933) from the box turtle Cuora amboinensis (Daudin) collected in Malaysia. In this redescription, we amend the original description by noting that there are only four cephalic papillae and that there are five pairs of post-anal papillae, and propose that the name of this species be corrected from S. octorugatus to S. octorugatum. Additionally, we removed the tissues overlying the buccal capsule and have used SEM studies to show that the peribuccal shields extend laterally from the buccal capsule, forming a surface possibly used in muscle attachment. Furthermore, we show that the supposedly noncuticularised cylinder connecting the buccal capsule to the oesophagus in the Camallanidae is part of the buccal capsule and is, therefore, likely to be cuticularised. We also examine morphological measurements of taxonomic interest for correlations with total body length and find that many characters traditionally used for inter-and intraspecific comparisons are correlated with total body length in adult female worms. This suggests that comparisons between samples of adult female worms that do not account for the potential effect of total body length may be misleading. However, we show that some features of taxonomic interest are not correlated with total body length

Prokaryotic Heme Biosynthesis: Multiple Pathways to a Common Essential Product

The advent of heme during evolution allowed organisms possessing this compound to safely and efficiently carry out a variety of chemical reactions that otherwise were difficult or impossible. While it was long assumed that a single heme biosynthetic pathway existed in nature, over the past decade, it has become clear that there are three distinct pathways among prokaryotes, although all three pathways utilize a common initial core of three enzymes to produce the intermediate uroporphyrinogen III. The most ancient pathway and the only one found in the Archaea converts siroheme to protoheme via an oxygen-independent four-enzyme-step process. Bacteria utilize the initial core pathway but then add one additional common step to produce coproporphyrinogen III. Following this step, Gram-positive organisms oxidize coproporphyrinogen III to coproporphyrin III, insert iron to make coproheme, and finally decarboxylate coproheme to protoheme, whereas Gram-negative bacteria first decarboxylate coproporphyrinogen III to protoporphyrinogen IX and then oxidize this to protoporphyrin IX prior to metal insertion to make protoheme. In order to adapt to oxygen-deficient conditions, two steps in the bacterial pathways have multiple forms to accommodate oxidative reactions in an anaerobic environment. The regulation of these pathways reflects the diversity of bacterial metabolism. This diversity, along with the late recognition that three pathways exist, has significantly slowed advances in this field such that no single organism's heme synthesis pathway regulation is currently completely characterized

Distributed Cognition in Cancer Treatment Decision Making: An Application of the DECIDE Decision-Making Styles Typology

Distributed cognition occurs when cognitive and affective schemas are shared between two or more people during interpersonal discussion. Although extant research focuses on distributed cognition in decision making between health care providers and patients, studies show that caregivers are also highly influential in the treatment decisions of patients. However, there are little empirical data describing how and when families exert influence. The current article addresses this gap by examining decisional support in the context of cancer randomized clinical trial (RCT) decision making. Data are drawn from in-depth interviews with rural, Appalachian cancer patients (N = 46). Analysis of transcript data yielded empirical support for four distinct models of health decision making. The implications of these findings for developing interventions to improve the quality of treatment decision making and overall well-being are discussed

Distributed Cognition in Cancer Treatment Decision Making: An Application of the DECIDE Decision-Making Styles Typology

Distributed cognition occurs when cognitive and affective schemas are shared between two or more people during interpersonal discussion. Although extant research focuses on distributed cognition in decision making between health care providers and patients, studies show that caregivers are also highly influential in the treatment decisions of patients. However, there are little empirical data describing how and when families exert influence. The current article addresses this gap by examining decisional support in the context of cancer randomized clinical trial (RCT) decision making. Data are drawn from in-depth interviews with rural, Appalachian cancer patients (N = 46). Analysis of transcript data yielded empirical support for four distinct models of health decision making. The implications of these findings for developing interventions to improve the quality of treatment decision making and overall well-being are discussed