Phenol degradation by a psychrotrophic strain of Pseudomonas putida

Summary Cell growth and phenol degradation kinetics were studied at 10°C for a psychrotrophic bacterium, Pseudomonas putida Q5. The batch studies were conducted for initial phenol concentrations, S_o, ranging from 14 to 1000 mg/1. The experimental data for 14<=S_o<=200 mg/1 were fitted by non-linear regression to the integrated Haldane substrate inhibition growth rate model. The values of the kinetic parameters were found to be: _m=0.119 h^–1, K _S=5.27 mg/1 and K _I=377 mg/1. The yield factor of dry biomass from substrate consumed was Y=0.55. Compared to mesophilic pseudomonads previously studied, the psychrotrophic strain grows on and degrades phenol at rates that are ca. 65–80% lower. However, use of the psychrotrophic microorganism may still be economically advantageous for waste-water treatment processes installed in cold climatic regions, and in cases where influent waste-water temperatures exhibit seasonal variation in the range 10–30°C.Nomenclature K _S saturation constant (mg/l) - K _I substrate inhibition constant (mg/l) - specific growth rate (h^–1) - _m maximum specific growth rate without substrate inhibition (h^–1) - _max maximum achievable specific growth rate with substrate inhibition (h^–1) - S substrate (phenol) concentration (mg/l) - S_o initial substrate concentration (mg/l) - S_max substrate concentration corresponding to _max (mg/l) - t time (h) - X cell concentration, dry basis (mg DW/l) - X_f final cell concentration, dry basis (mg DW/l) - X_o initial cell concentration, dry basis (mg DW/l) - Y yield factor (mg DW cell produced/mg substrate consumed)     

Purification of ribulose 1,5-bisphosphate carboxylase/oxygenase and of carboxysomes from Thiobacillus thyasiris the putative symbiont of Thyasira flexuosa (Montagu)

The bacterial symbionts of many marine invertebrates contain ribulose 1,5-bisphosphate (RuBP) carboxylase but apparently no carboxysomes, polyhedral bodies containing RuBP carboxylase. In the few cases where polyhedral bodies have been observed they have not been characterised enzymatically. Polyhedral bodies, 50–90 nm in diameter, were observed in thin cell sections of Thiobacillus thyasiris the putative symbiont of Thyasira flexuosa and RuBP carboxylase activity was detected in both soluble and particulate fractions after centrifugation of cell-free extracts. RuBP carboxylase purified 90-fold from the soluble fraction was of high molecular weight and consisted of large and small subunits, with molecular weights of 53,110 and 11,100 respectively. Particulate RuBP carboxylase activity was associated with polyhedral bodies 50–100 nm in diameter, as revealed by density gradient centrifugation and electron microscopy. Therefore, the polyhedral bodies were inferred to be carboxysomes. Native electrophoresis of isolated carboxysomes demonstrated a major band which comigrated with the purified RuBP carboxylase and three minor bands of lower molecular weight. Sodium dodecyl-sulphate (SDS) gel electrophoresis of SDS-dissociated carboxysomes demonstrated nine major polypeptides two of which were the large and small subunits of RuBP carboxylase. The RuBP carboxylase subunits represented 21% of the total carboxysomal protein. The most abundant polypeptide had a molecular weight of 40,500. Knowledge of carboxysome composition is necessary to provide an understanding of carboxysome function.Abbreviations FPLC fast performance liquid chromatography - IB isolation buffer - PAGE polyacrylamide gel electrophoresis - RuBP carboxylase - ribulose 1,5-bisphosphate carboxylase/oxygenase - SDS sodium dodecyl-sulphate     

Codon usage and G+C content in Bradyrhizobium japonicum genes are not uniform

To date, the sequences of 45 Bradyrhizobium japonicum genes are known. This provides sufficient information to determine their codon usage and G+C content. Surprisingly, B. japonicum nodulation and NifA-regulated genes were found to have a less biased codon usage and a lower G+C content than genes not belonging to these two groups. Thus, the coding regions of nodulation genes and NifA-regulated genes could hardly be identified in codon preference plots whereas this was not difficult with other genes. The codon frequency table of the highly biased genes was used in a codon preference plot to analyze the RSRj9 sequence which is an insertion sequence (IS)-like element. The plot helped identify a new open reading frame (ORF355) that escaped previous detection because of two sequencing errors. These were now corrected. The deduced gene product of ORF355 in RSRj9 showed extensive similarity to a putative protein encoded by an ORF in the T-DNA of Agrobacterium rhizogenes. The DNA sequences bordering both ORFs showed inverted repeats and potential target site duplications which supported the assumption that they were IS-like elements.     

Phage resistance and altered growth habit in a strain of Streptococcus bovis

Bacteriophage (phi Sb01) of Streptococcus bovis, isolated from pooled rumen fluid of cattle, was a small siphovirus of morphotype B1. It contained double-stranded DNA of length 30.9 kb, which was digested by the restriction endonucleases, EcoRI, HindIII, and PvuII. Bacteria which survived phi Sb01 infection (strain 2BAr) grew in long chains (100-200 cells), ultimately forming large clumps of cells. This growth habit was in distinct contrast to that of the parent host strain which grew predominantly in the form of single cells or diplococci. Strain 2BAr was genetically stable, resistant to phi Sb01 attack, and the observed differences in the growth characteristics of the parent strain and 2BAr indicated that cells of 2BAr were more adherent. In the rumen ecosystem, the selection of phage-resistant bacteria with altered growth characteristics may be a factor in modifying bacterial phenotypes, and thus increasing variability among bacteria which are closely related genetically.     

Molecular detection of microscopic and submicroscopic deletions associated with Miller-Dieker syndrome.

Miller-Dieker syndrome (MDS), a disorder manifesting the severe brain malformation lissencephaly ("smooth brain"), is caused, in the majority of cases, by a chromosomal microdeletion of the distal short arm of chromosome 17. Using human chromosome 17-specific DNA probes, we have begun a molecular dissection of the critical region for MDS. To localize cloned DNA sequences to the MDS critical region, a human-rodent somatic cell hybrid panel was constructed which includes hybrids containing the abnormal chromosome 17 from three MDS patients with deletions of various sizes. Three genes (myosin heavy chain 2, tumor antigen p53, and RNA polymerase II) previously mapped to 17p were excluded from the MDS deletion region and therefore are unlikely to play a role in its pathogenesis. In contrast, three highly polymorphic anonymous probes, YNZ22.1 (D17S5), YNH37.3 (D17S28), and 144-D6 (D17S34), were deleted in each of four patients with visible deletions, including one with a ring chromosome 17 that is deleted for a portion of the single telomeric prometaphase subband p13.3. In two MDS patients with normal chromosomes, a combination of somatic cell hybrid, RFLP, and densitometric studies demonstrated deletion for YNZ22.1 and YNH37.3 in the paternally derived 17's of both patients, one of whom is also deleted for 144-D6. The results indicate that MDS can be caused by submicroscopic deletion and raises the possibility that all MDS patients will prove to have deletions at a molecular level. The two probes lie within a critical region of less than 3,000 kb and constitute potential starting points in the isolation of genes implicated in the severe brain maldevelopment in MDS.     

Inheritance of colour and coat in the Belgian Shepherd dog

The several colours and coats of the Belgian Shepherd dog are shown to be due primary to combinations of the following genes: dominant black (A ^s ), dominant yellow (A ^y ), chinchilla (ch), long hair (l) and wire hair (Wh). The gene for black and tan (a ^t ) is or has been present in the breed. All of the dominant yellow dogs exhibit a black facial mask and extensive suffusion of black guard hairs on the body.     

Experimental effects of elevated salinity on three benthic invertebrates in Pyramid Lake,Nevada

Salinity of Pyramid Lake increased from 3.7 to 5.5 between 1933 and 1980. Concern over future reductions in overall species richness prompted experiments to assess responses of dominant lake organisms to elevated salinity. Salinity tolerances of three important benthic invertebrates, Hyalella aztecta, Chironomus utahensis, and Heterocypris sp., were tested in controlled laboratory bioassays and also in a semi-natural environment consisting of large (47 m³) mesocosms.Densities of H. azteca in mesocosms were significantly lower at salinities of 8.0 and 11.0 compared with 5.6 controls in year one, but not in 8.5 salinity mesocosms in year two. The 96-h LC₅₀ for H. azteca was high at 19.5. Short-term mortalities of C. utahensis were 100% at salinities of 13.3 and greater. Fifty-seven percent fewer larvae matured from third to fourth instar at 8.9 than at 5.5 salinity in 17 day subacute bioassays. Furthermore, larval chironomid densities and emergence of adults from mesocosms were significantly reduced at salinities of 8.0 and higher compared with controls. Mortality of Heterocypris sp. was 50% at a salinity of 18.6 in laboratory bioassays and populations in mesocosms ranged between 40 and 100% lower at salinities of 8.0 and 11.0 than in controls.Multiple generation mesocosm experiments indicated all three invertebrates were more sensitive to elevated salinity than results of short-term bioassays. Our studies suggest populations of these invertebrates may be reduced from present levels if Pyramid Lake's salinity were to double, although none are expected to be extirpated. Food habit shifts and reduced production of lake fishes are likely consequences of salinity-induced disruption in the benthic invertebrate forage base.     

Phytoplankton and phosphorus in southern Georgian Bay, 1973–1982, and implications for phosphorus loading controls

The phytoplankton and nutrient status of the embayments between Penetanguishene and Waubaushene in southern Georgian Bay (Severn Sound) were examined during the ice-free periods of 1973–1982 because the area showed symptoms of excessive nutrient enrichment. Four wastewater treatment plants currently discharge to the area, another is under construction and a sixth plant has been proposed. Except for Penetang Bay, the area is well-mixed by prevailing winds but is somewhat isolated from the main part of Georgian Bay. Average phytoplankton biomasses throughout the area were 10–20× higher than values from adjacent Nottawasaga Bay where, during 1980, total phytoplankton biomass ranged between 0.15 and 0.25 mm³ · l^–1. Total phosphorus concentrations were highest in Penetang Bay, ranging between 30 and 49 µg P · l^–1 (May–September means) over the 10 year period. Phosphorus concentrations in Nottawasaga Bay averaged 4–6 µg P · l^–1 and no significant differences were detected among the sampling stations; however, phytoplankton densities at stations near urban centres and river inflows were significantly higher than at more remote offshore sites and attests to the use of phytoplankton as a sensitive measure of trophic status in Georgian Bay.Although improvement of Severn Sound water quality to a level comparable to that presently existing in Nottawasaga Bay may never be practical, steps are being taken to control high industrial phosphorus loading and to lessen bypassing of sewage treatment facilities previously hydraulically overloaded during periods of heavy runoff. These measures, along with an evaluation of other major sources of nutrients to Severn Sound, should enable a refinement of the nutrient management programme for Severn Sound and some improvement in trophic status.