Genome sequence of the emerging pathogen Helicobacter canadensis.

We determined the genome sequence of the type strain of Helicobacter canadensis, an emerging human pathogen with diverse animal reservoirs. Potential virulence determinants carried by the genome include systems for N-linked glycosylation and capsular export. A protein-based phylogenetic analysis places H. canadensis close to Wolinella succinogenes.

Metabolite production and growth efficiency.

The capacity to sustain the large fluxes of carbon and energy required for rapid metabolite production appears to be inversely related to the growth efficiency of micro-organisms. From an overall energetic point of view three main classes of metabolite may be distinguished. These are not discrete categories, as the energetics of biosynthesis will depend on the precise biochemical pathways used and the nature of the starting feed stock(s). (1) For metabolites like exopolysaccharides both the oxidation state and the specific rate of production appear to be inversely related to the growth efficiency of the producing organism. Maximum rates of production are favored when carbon and energy flux are integrated, and alteration of this balance may negatively effect production rates. (2) The production of metabolites like organic acids and some secondary metabolites results in the net production of reducing equivalents and/or ATP. It is thought that the capacity of the organism to dissipate this product-associated energy limits its capacity for rapid production. (3) For metabolites like biosurfactants and certain secondary metabolites that are composed of moieties of significantly different oxidation states production from a single carbon source is unfavorable and considerable improvements in specific production rate and final broth concentration may be achieved if mixed carbon sources are used. By careful selection of production organism and starting feedstock(s) it may be possible to tailor the production, such that the adverse physiological consequences of metabolite overproduction on the production organism are minimized.

The kinetics and physiology of stipitatic acid and gluconate production by carbon sufficient cultures of Penicillium stipitatum growing in continuous culture.

The yield from glucose of ammonia-grown carbon-limited continuous cultures of Penicillium stipitatum was ca. 20% higher than that of nitrate-grown cultures at all growth rates examined. However, the yield from oxygen was similar during growth on both nitrogen sources. Under phosphate limitation the specific rate of gluconic acid and stipitatic acid production increased with growth rate, but the former product accounted for virtually 100% of the excreted carbon. Stipitatic acid was not produced under nitrogen limitation, and glucose supplied to the culture in excess of that required for growth was virtually quantatively converted into gluconic acid. Productivities of 11.4 g gluconic acid/L/h were stably maintained in continuous culture. Under conditions of glucose excess the enzyme glucose oxidase was excreted into the culture. The specific activity of this extracellular enzyme increased when the input glucose concentration to the culture was progressively increased. The excretion of a protein under nitrogen limitation suggests that this enzyme plays an important role under these conditions. Indeed, it was demonstrated that nitrogen-limited cultures did not overmetabolize gluconate at either pH 6.5 or 3.5, although up to 29 g/L gluconate was present in the culture. The Y(gluconate) and YO(2) of C- and N-limited gluconate-grown cultures were similar indicating that the rapid conversion of glucose to gluconate probably affords a means of regulating carbon flow in this organism. Nitrogen-limited cultures of P. stipitatum overmetabolized glucose to a much greater extent than acetate, fructose, or gluconate.

The effects of cyanide on the growth and respiration of Enterobacter aerogenes in continuous culture.

The effect of cyanide on the physiology of lactate- and oxygen-limited Enterobacter aerogenes NCTC 10336 was studied in chemostat culture (D = 0.1 h-1). In the absence of cyanide, the molar growth yield from oxygen (YO2) under oxygen limitation was 60% of the carbon-limited value. A similar decrease in yield was observed in a lactate-limited culture (excess oxygen) which was continuously fed low concentrations of potassium cyanide. The cultures with the lower growth yields possessed respiratory systems less sensitive to inhibition by cyanide. This was particularly marked in cultures grown in the presence of cyanide. Increased cyanide resistance was associated with an increase in the concentration of a cytochrome oxidase tentatively identified as a d-type and the appearance of additional cytochromes tentatively identified as b-type.

The occurrence and identification of intracellular polyglucose storage granules in Methylococcus NCIB 11083 grown in chemostat culture on methane.

The accumulation of intracellular storage granules (0.03--0.5 micrometer) by Methylococcus NCIB 11083 when grown under conditions of ammonia limitation with methane as the sole source of carbon and energy was inversely proportional to the dilution rate. The isolated material was composed entirely of glucose residues and the infra-red spectrum exhibited characteristic absorption bands at 925 cm(-1), 845 cm(-1) and 745 +/- 4cm(-1), indicating the presence of alpha (1 leads to 4) glycosidic linkages. The polymer dissolved in hot water to give an opalescent solution that formed a violet iodine complex with an absorption maximum at 550nm, identical to that observed with reference amylopectin. The percentage of the polysaccharide released as maltose by the action of beta- and alpha-amylases was 55--64% and 80--90% respectively, values very similar to those obtained by the action of these enzymes on reference amylopectin and glycogen. Methylation analysis indicated that the average interior and exterior chain lengths of the polymer were 2.7 and 10.0 glucose units respectively and confirmed that the Methylococcus polyglucose is a branched polymer composed of units joined by 1 leads to 4 and 1 leads to 6 linkages. The number average molecular weight of the polymer is 2--4.5 x 10(5). The stored polymer was metabolised by the organism and its metabolism resulted in the synthesis of protein.

Molar growth yields, respiration and cytochrome profiles of Beneckea natriegens when grown under carbon limitation in a chemostat.

The effect of growth rate on the physiology of Beneckea natriegens was studied in chemostat culture. The molar growth yields (Y) from glucose and oxygen, the specific rates of oxygen (Qo2) and glucose (Qg1c) consumption and the specific rate of CO2 production (Qco2) were linearly dependent on the growth rate over the dilution rate 0.17 h-1 to 0.60 h-1. Further increase in the dilution rate resulted in a decrease in growth yield and respiration rate and these changes were coincident with increases in the specific rate of glucose utilisation and of acetate production. The affinity of Beneckea natriegens for glucose was similar when measured either directly in chemostat culture or in a closed oxygen electrode system using harvested bacteria. The total content of cytochromes decreased with increasing growth rate. However, the quantity of CO-binding cytochromes remained independent of growth rate and correlated with the potential respiration rate.

Molar growth yields, respiration and cytochrome patterns of Beneckea natriegens when grown at different medium dissolved-oxygen tensions.

The effect of medium dissolved-oxygen tension on the molar growth yield, respiration and cytochrome content of Beneckea natriegens in chemostat culture (D 0-37 H-1) was examined. The molar growth yield (Y), the specific rate of oxygen (qo2) and glucose consumption, and the specific rate of carbon dioxide evolution were independent of the dissolved-oxygen tension above a critical value (greatest than 2 mmHg). However, the potential respiration rate increased with reduction in the dissolved-oxygen tension at values of the dissolved-oxygen tension well above the critical value. Changes in the cytochrome content occurred at dissolved-oxygen tensions well above the critical value. An increase in cytochrome c relative to cytochrome b was observed as the dissolved-oxygen tension was decreased. Reduction of the dissolved-oxygen tension to less than I mmHg caused a switch to fermentative metabolism shown by the apparent rise in YO2 and decrease in the molar growth yield from glucose. At this point the potential respiration rate (qO2) increased to its highest value, while the cytochrome pattern reverted to that observed at dissolved-oxygen tensions above 96 mmHg. There appeared to be no correlation between cytochrome content, potential qO2, in situ qO2, and cyanide sensitivity of the organism at various dissolved-oxygen tensions.

Urinary and faecal Escherichia coli O-sero-groups in symptomatic urinary-tract infection and asymptomatic bacteriuria.

The degree of correspondence between urinary and faecal Escherichia coli O-groups has been assessed in non-pregnant women with symptomatic urinary-tract infection or asymptomatic bacteriuria. In 20 of 26 patients with symptomatic urinary tract infection E. coli of the same O-groups as that of the urinary infecting strain was also present in the patient's faecal flora of only five of 25 patients with asymptomatic bacteriuria. This finding indicates that the majority of episodes of symptomatic urinary tract infection in non-pregnant women are not preceded by a significant period of asymptomatic bacteriuria. E. coli O6 showed correspondence between urinary and faecal isolates more frequently than did other O-groups, but it had a relatively low prevalence in the faecal flora of patients with urinary-tract infection caused by E. coli of other O-groups. This finding lends support to previous suggestions that E. coli O6 may be especially pathogenic for the urinary tract.