Barnacle larval destination: piloting possibilities by bacteria and lectin interaction

Modulation of metamorphosis in barnacles in response to cues of biological origin is established. The bacteria associated with the barnacles also have a role in such modulations. We isolated the bacteria, Pseudomonas aeruginosa, Bacillus pumilus and Citrobacter freundii from the shell surface of Balanus amphitrite and assayed against its cypris larvae. The former species was promotory while the latter two inhibited cyprid metamorphosis. P. aeruginosa however, when tagged with lectins specific to glucose and its derivatives, mannose and fructofuranose negated the promotory effect. Whereas, tagging of galactose derivatives translated the inhibitory effect of B. pumilus and C. freundii into a promotory one showing that lectins can alter the signals in either direction. Galactose-binding lectins have been identified in the haemolymph of barnacles, which could find their way through the excretory system to the surface. The presence of such lectins could probably provide this organism with an ability to alter the signals or cues. Microscale patchiness of bacteria is also evident on surfaces in the sea. The availability of conflicting cues in patches may help pilot the larvae to their settlement destination. Understanding these controlling mechanisms and interfering with the pathways that are involved in lectin synthesis would be a step forward in antifouling technology.     

3-Methylaspartate ammonia-lyase as a marker enzyme of the mesaconate pathway for (S)-glutamate fermentation in Enterobacteriaceae

The enzyme 3-methylaspartase (3-methylaspartate ammonia-lyase, EC 4.3.1.2) was found in the cells of enteric bacteria, especially in the genera Citrobacter and Morganella, that were grown under anoxic and oxygen-limited conditions. The enzymes were purified to homogeneity from the cell-free extracts of 18 active strains and had similar enzymological properties such as action on columns, specific activity, molecular weight, subunit structure, and N-terminal amino acid sequence similarity. The production of the enzyme was dependent on the limitation of oxygen during growth and was arrested by aeration. The addition of external electron acceptors such as dimethylsulfoxide could support cell growth and production of the enzyme. Activities of glutamate mutase (EC 5.4.99.1) and (S)-citramalate hydrolyase (EC 4.2.1.34), key enzymes of the mesaconate pathway of (S)-glutamate fermentation in the genus Clostridium, were detected in the cells of the active strains grown under oxygen-limited conditions. Based on the results, the mesaconate pathway is proposed to explain the (S)-glutamate fermentation process observed in Enterobacteriaceae, and 3-methylaspartase could be a marker enzyme for this pathway. Received: 28 May 1997 / Accepted: 16 July 1997     

Re-Speciation of the Original Reference Strains of Serovars in the Citrobacter freundii (Bethesda-Ballerup Group) Antigenic Scheme of West and Edwards

The antigenic scheme for the Bethesda-Ballerup group of bacteria established by West and Edwards in 1954 has continued to be applied as a serotyping scheme for Citrobacter freundii. In 1993, however, the classification of the Citrobacter was drastically revised and the species C. freundii redefined by Brenner et al. Accordingly, to judge the propriety to continuously use a single antigenic scheme for the C. freundii complex, the 90 reference strains listed in the antigenic scheme for C. freundii by West and Edwards were characterized phenotypically and specified based on the revised classification. Of these 90 strains, two strains of Hafnia alvei and one of Escherichia coli were found. Among the remaining 87 reference strains, Citrobacter youngae was the predominant species (40 strains), followed by Citrobacter braakii (25 strains), Citrobacter werkmanii (13 strains), and the unnamed Citrobacter genospecies 10 of Brenner et al (six strains). Citrobacter freundii, as redefined, accounted for only three strains and ranked behind the other four species. No overlapping with most of the 42 O-groups and 82 H-antigens was recognized between species with few exceptions. O-groups 1–9 inclusive, which were estimated to represent more than 90% of the former C. freundii strains, occurred in strains of C. youngae and C. braakii; and all nine strains of O-group 29, formerly known as the Ballerup group, were identified as C. braakii. These findings suggest that further study of the serotyping system is needed for all H₂S-producing Citrobacter species.     

The novel gene trs1 encodes an essential protein for the transition from mitotic cell cycle to resting state in Schizosaccharomyces pombe

A novel gene trs1 in the fission yeast Schizosaccharomyces pombe has been genetically defined. The trs1 mutant showed several intriguing phenotypes. Cells were sensitive to starvation and rapidly lost viability in the stationary phase; cells in the stationary phase were sensitive to heat shock. Some heat-shock proteins were not induced and the heat-shock response in log-phase cells was defective. These mutant phenotypes strongly suggest a vital function of the trs1 gene product for transition from the G1 to G0 phase on starvation and for the normal heat-shock response.     

Phosphatase-mediated heavy metal accumulation by a Citrobacter sp. and related enterobacteria

Abstract A Citrobacter sp. was reported previously to accumulate heavy metals as cell-bound heavy metal phosphates. Metal uptake is mediated by the activity of a periplasmic acid-type phosphatase that liberates inorganic phosphate to provide the precipitant ligand for heavy metals presented to the cells. Amino acid sequencing of peptide fragments of the purified enzyme revealed significant homology to the phoN product (acid phosphatase) of some other enterobacteria. These organisms, together with Klebsiella pneumoniae , previously reported to produce acid phosphatase, were tested for their ability to remove uranium and lanthanum from challenge solutions supplemented with phosphatase substrate. The coupling of phosphate liberation to metal bioaccumulation was limited to the metal accumulating Citrobacter sp.; therefore the participation of species-specific additional factors in metal bioaccumulation was suggested.     

Nucleoside synthesis by immobilised bacterial whole cells

Biocatalysed synthesis of nucleosides was carried out using immobilised whole cells of Escherichia coli ATCC 47092, Enterobacter gergoviae CECT 857 and Citrobacter amalonaticus CECT 863. The synthesis of adenosine from uridine was used as reaction model to test the biocatalysts. Reactions were carried out using non-growing cells. Maximum activity was obtained with cells harvested at the beginning of the stationary phase. Immobilization by whole cell entrapment was employed using different matrix such as alginate, agar, agarose and polyacrylamide. The percentage of monomer, the shaking speed, the catalyst load and nature of the matrix were optimized. In the first reutilization cycle, similar yields (80–95%) were obtained with both free and immobilized cells in the reaction model, although in the last case, longer reaction times were necessary. The immobilized cells can be reused at least for more than 30 times without significant loss of the catalytic activity. The immobilized biocatalysts have been used in the synthesis of different nucleosides.     

Design of new primers that can detect Salmonella without decrease of detection threshold in the presence of contaminant organisms

Novel PCR primer sets for the detection of Salmonella were designed based on the oriC sequence information of various enteric bacteria, which are potential contaminants in commercial liquid egg samples. Using the PCR primers, the selective detection of Salmonella in the presence of large excess number of salmonella-like strains were achieved without the reduction of its sensitivity. The application of these primer sets for the detection of Salmonella from commercial liquid egg was also demonstrated.     

The structure of the lipopolysaccharide core region of Citrobacter 027

The structure of Citrobacter 027 lipopolysaccharide core has been established using sugar and methylation analyses and 1H-NMR spectroscopy, and was shown to be identical to the core described recently in PCM 1487 strain which represents a separate serotype in Citrobacter genus.     

Iron utilization studies in Citrobacter species

Abstract Seventy-one strains of Citrobacter were screened for iron scavenging mechanisms by biologic and chemical assays. Essentially all citrobacteria (70 / 71) were found to elaborate enterobactin-like siderophores by both biologic and chemical assays, however only C. koseri (C. diversus) was found to produce aerobactin. The concentration of ethylenediamine di( o -hydroxyphenylacetic acid) (EDDA) required to inhibit the growth of individual Citrobacter strains by depleting free iron ranged from 250 μg/ml to 1000 μg/ml. Iron utilization studies of selected Citrobacter isolates indicated that hemin and hematin could reverse the effects of iron limitation on growth under iron-stressed conditions (1000 μg/ml of EDDA). Two C. koseri strains grown under iron-restricted conditions showed similar changes in their whole cell protein profiles including induction of high molecular mass proteins (72–83 kDa) which may play a role in iron acquisition under iron-stressed conditions. The collective results support an additional virulence-associated mechanism for C. koseri strains which may help explain the greater pathogenic potential this group has for causing serious extraintestinal disease in humans.