Ancestral cyanobacteria are assumed to be prominent primary producers after the Great Oxidation Event [≈2.4 to 2.0 billion years (Ga) ago], but carbon isotope fractionation by extant marine cyanobacteria (α-cyanobacteria) is inconsistent with isotopic records of carbon fixation by primary producers in the mid-Proterozoic eon (1.8 to 1.0 Ga ago). To resolve this disagreement, we quantified carbon isotope fractionation by a wild-type planktic β-cyanobacterium (Synechococcus sp. PCC 7002), an engineered Proterozoic analog lacking a CO2-concentrating mechanism, and cyanobacterial mats. At mid-Proterozoic pH and pCO2 values, carbon isotope fractionation by the wild-type β-cyanobacterium is fully consistent with the Proterozoic carbon isotope record, suggesting that cyanobacteria with CO2-concentrating mechanisms were apparently the major primary producers in the pelagic Proterozoic ocean, despite atmospheric CO2 levels up to 100 times modern. The selectively permeable microcompartments central to cyanobacterial CO2-concentrating mechanisms (“carboxysomes”) likely emerged to shield rubisco from O2 during the Great Oxidation Event.

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Carboxysomes, prototypical bacterial microcompartments (BMCs) found in cyanobacteria, are large (~1 GDa) and essential protein complexes that enhance CO2 fixation. While carboxysome biogenesis has been elucidated, the activity dynamics, lifetime, and degradation of these structures have not been investigated, owing to the inability of tracking individual BMCs over time in vivo. We have developed a fluorescence-imaging platform to simultaneously measure carboxysome number, position, and activity over time in a growing cyanobacterial population, allowing individual carboxysomes to be clustered on the basis of activity and spatial dynamics. We have demonstrated both BMC degradation, characterized by abrupt activity loss followed by polar recruitment of the deactivated complex, and a subclass of ultraproductive carboxysomes. Together, our results reveal the BMC life cycle after biogenesis and describe the first method for measuring activity of single BMCs in vivo.

Cyanobacterial carboxysomes encapsulate carbonic anhydrase and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). Genetic deletion of the major structural proteins encoded within the ccm operon in Synechococcus sp. PCC 7002 (ΔccmKLMN) disrupts carboxysome formation and significantly affects cellular physiology. Here we employed both metabolite pool size analysis and isotopically nonstationary metabolic flux analysis (INST-MFA) to examine metabolic regulation in cells lacking carboxysomes. Under high CO2 environments (1%), the ΔccmKLMN mutant could recover growth and had a similar central flux distribution as the control strain, with the exceptions of moderately decreased photosynthesis and elevated biomass protein content and photorespiration activity. Metabolite analyses indicated that the ΔccmKLMN strain had significantly larger pool sizes of pyruvate (> 18 folds), UDPG (uridine diphosphate glucose), and aspartate as well as higher levels of secreted organic acids (e.g., malate and succinate). These results suggest that the ΔccmKLMN mutant is able to largely maintain a fluxome similar to the control strain by changing in intracellular metabolite concentrations and metabolite overflows under optimal growth conditions. When CO2 was insufficient (0.2%), provision of acetate moderately promoted mutant growth. Interestingly, the removal of microcompartments may loosen the flux network and promote RuBisCO side-reactions, facilitating redirection of central metabolites to competing pathways (i.e., pyruvate to heterologous lactate production). This study provides important insights into metabolic regulation via enzyme compartmentation and cyanobacterial compensatory responses.

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A total of 2308 mid-trimester terminations using PGE, extraamniotically (1608) or intra-amniotically (700) has been analysed for efficacy and immediate and early morbidity. 'The mean induction-toabortion intervals were similar for the two routes. Overall. 67% of the patients werc in hospital for 1 night. Morbidity rates were similar for the two administration routes and were no higher than those reported for second trimester terminations using dilatation and evacuation. Minor side-effects of vomiting occurred in 1006 (44%) and diarrhoea in 320 (Idyo). Forty (1.7y0) lost more than 500 ml of blood during termination and 13 (0.6%) were transfused. Major complications were extremely rare and genital tract trauma only occurred in 4 (0.17%) and proven pelvic infection in 2 (0.08%) patients. Thirty-three (1.4%) were readmitted and required a surgical evacuation of the uterus. Since longterm complications have been assessed for this method of termination and found to be infrequent, we see no reason to consider a change in methods for second trimester terminations.

Study objective To assess the safety and patient satisfaction of laparoscopic subtotal hysterectomy (LSH) using a standardised surgical technique.Design Prospective observational study.Setting Princess Royal University Hospital, Chelsfield Park Hospital and Sloane Hospital, Kent, UK.Patients and materials Four hundred consecutive women with menorrhagia underwent LSH. The procedure was performed using the Plasma Kinetic Bipolar Diathermy (Gyrus International Ltd, Berkshire, UK) for pedicle ligation and the Lap Loop system (Roberts Surgical Healthcare Ltd, Kidderminster, UK) to detach the cervix. An electromechanical morcellator (Morcellex; Ethicon Women's Health and Urology, Cincinnati, OH, USA) was used to remove the uterus from the abdominal cavity.Main outcome measures Patient satisfaction, morbidity rates and readmission rates.Results A total of 400 LSH were performed between February 2003 and November 2006. The principal clinical indication for hysterectomy was menorrhagia. The mean duration of surgery was 46.4 minutes. The mean operative blood loss was 126 ml. Concurrent surgery was performed in 141 women. Minor and major perioperative complications were encountered in 5% (n = 20) of women. The major complication rate was 1.2% (n = 5): three women (0.75%) with bladder perforation, two women (0.5%) with bowel injury and one woman (0.25%) with a vesicocervical fistula. Eight women (2%) suffered from cyclical vaginal bleeding postoperatively.Conclusions LSH is a safe and effective treatment for menorrhagia and other menstrual disorders when hysterectomy is indicated. Women appreciate the quick recovery period, reduced time off work and faster return to normal activity. Our data suggest that LSH can replace abdominal hysterectomy in selected cases.