Cloning and characterization of an extracellular temperature-labile serine protease gene from Aeromonas hydrophila

Aeromonas virulence is thought to depend on multigenic functions. The gene for an extracellular protease from Aeromonas hydrophila SO2/2 was cloned in Escherichia coli C600-1 by using pIJ860, bifunctional plasmid, as a vector. The gene encodes for a temperature-labile serine protease (P2) with a molecular mass of approx. 68 kDa which is highly inhibited by PMSF. The gene was expressed in Streptomyces lividans 1326 by transforming protoplasts with the original clone pPA2. We were also able to transfer and express the prt P2 gene in Pseudomonas putida by mating experiments. The protein P2 was secreted into the periplasms of both P. putida and E. coli C600-1 being identical in properties to one of the proteases secreted into the culture supernatant by A. hydrophila SO2/2.     

Functional aspects of ano-rectal vascularity

The blood supply of the ano-rectum has been studied in cadaveric specimens by angiographic methods. The vascular anastomosis between the middle rectal and superior rectal vessels was found to be demonstrable on one side only. There appears to be a midline paucity of vessels in both the posterior and anterior rectal walls, and this may be important in the aetiology of anastomotic dehiscence in low anterior resection.     

Activity expressed from cloned Anacystis nidulans large and small subunit ribulose bisphosphate carboxylase genes

Summary The ribulose bisphosphate carboxylase/oxygenase (EC4.1.1.39) (RubisCO) large and small subunit genes from Anacystis nidulans have been cloned as a single fragment into M 13mp10 and pEMBL8 and expressed in Escherichia coli. From M 13mp10 a low yield of enzyme with high specific activity was obtained. The molecular weight of the active enzyme was 260 000 Da and of the inactive enzyme approximately 730 000 Da. The small and large subunits cloned separately did not express activity. The RubisCO gene cloned into pEMBL8 expressed activity up to 22 times that from the M 13 cloned RubisCO DNA. The RubisCO protein produced by the pEMBL cloned gene had a normal MW (550 000). Immunoprecipitation and polyacrylamide gel electrophoresis showed the presence of both large and small subunits.     

Factors influencing algal species assemblages on reef and cobble substrata off Ghana

Subtidal algal assemblages were studied on two substrata, rocky reefs and calcareous cobbles. Although the two occur together at comparable depths, their vegetation differs in species composition and richness, and in patterns of plant size, life form, and longevity. The reef bears a species-rich, patchy cover of small filamentous and crustose forms, with occasional clumps of more robust species. The cobbles support a sparse cover of large leafy and dendritic species in addition to many of the smaller species found on the reef. The floristic separation arises from differential establishment and survival of species under conditions of (1) grazing by fish and urchins (on the reef only), and (2) seasonal physical disturbance during storms leading to the removal of most algae (on the cobbles only). Both substrata show a seasonal floristic cycle, but the trend is more pronounced on cobbles. Species do not depart from randomness in their patterns of co-occurrence on individual cobbles or reef fragments. Interspecific competition appears comparatively unimportant in determining species composition on either substratum.     

Cassava leaves as human food

The use of cassava leaves as human food is reviewed and their value as a source of protein and vitamins for supplementing predominantly starchy diets reemphasized. The problem of the toxicity of the leaves is considered, and the effects on both nutritive value and toxicity of the traditional methods of preparing the leaves, such as drying, pounding, and long periods of boiling, are described and discussed. Loss of nutrients, particularly vitamins, occurs during processing but remaining levels can still make an important contribution to the diet. HCN levels are reduced considerably by the processing methods, although the toxic effects of residual levels need further investigation.     

The relationship of protein and lipid synthesis during the biogenesis of mitochondrial membranes

Summary Rat liver mitochondria were fractionated into inner and outer membrane components at various times after the intravenous injection of¹⁴C-leucine or¹⁴C-glycerol. The time curves of protein and lecithin labeling were similar in the intact mitochondria, the outer membrane fraction, and the inner membrane fraction. In rat liver slices also, the kinetics of³H-phenylalanine incorporation into mitochondrial KCl-insoluble proteins was identical to that of¹⁴C-glycerol incorporation into mitochondrial lecithin. These results suggest a simultaneous assembly of protein and lecithin during membrane biogenesisThe proteins and lecithin of the outer membrane were maximally labeledin vivo within 5 min after injection of the radioactive precursors, whereas the insoluble proteins and lecithin of the inner membrane reached a maximum specific acitivity 10 min after injection.Phospholipid incorporation into mitochondria of rat liver slices was not affected when protein synthesis was blocked by cycloheximide, puromycin, or actinomycin D. The injection of cycloheximide 3 to 30 min prior to¹⁴C-choline did not affect thein vivo incorporation of lecithin into the mitochondrial inner or outer membranes; however treatment with the drug for 60 min prior to¹⁴C-choline resulted in a decrease in lecithin labeling. These results suggest that phospholipid incorporation into membranes may be regulated by the amount of newly synthesized protein available.When mitochondria and microsomes containing labeled phospholipids were incubated with the opposite unlabeled fractionin vitro, a rapid exchange of phospholipid between the microsomes and the outer membrane occurred. A slight exchange with the inner membrane was observed.