Alterations in the major heterotrophic bacterial populations isolated from a still bottled mineral water

M orais , P.V. & D a C osta , M.S. 1990. Alterations in the major heterotrophic bacterial populations isolated from a. still bottled mineral water. Journal of Applied Bacteriology 69 , 750–757.
The heterotrophic bacterial population of a bottled mineral water stored in returnable glass bottles and in polyvinyl chloride (PVC) bottles at room temperature was studied over 9–12 months. The plate counts in R₂A medium incubated at 22 and 37C were low initially, increasing to 10⁴-10⁵ cfu/ml within a few days of bottling. The number of bacteria recovered at 22C from PVC bottles was fairly constant during the storage period, but the population isolated at 37C decreased markedly after storage for 1 year. The major components of the population were Pseudomonas strains, one of which was identified as Pseudomonas vesicularis . Major changes took place during storage; two groups of bacteria (B and C) were dominant initially, but during the latter period of storage other groups (F, G and H) increased in number.     

Modulation of maize roots H+-ATPase by sulfated polysaccharides

Vesicles derived from maize roots retain a membrane bound H⁺-ATPase that is able to pump H⁺ at the expense of ATP hydrolysis. In this work it is shown that heparin, fucose-branched chondroitin sulfate and dextran sulfate 8000 promote a shift of the H⁺-ATPase optimum pH from 6.0 to 7.0. This shift is a result of a dual effect of the sulfated polysaccharides, inhibition at pH 6.0 and activation at pH 7.O. At pH 6.0 dextran 8000 promotes an increase of the apparent K_m for ATP from 0.28 to 0.95 mM and a decrease of the V_max from 14.5 to 7.1 mol P_i/mg · 30 min^–1. At pH 7.0 dextran 8000 promotes an increase in V_max from 6.7 to 11.7 mol Pi/mg · 30 min^–1. In the presence of lysophosphatidylcholine the inhibitory effect of the sulfated polysaccharides observed at pH 6.0 was not altered but the activation of pH 7.0 decreased. It was found that in the presence of sulfated polysaccharides the ATPase became highly sensitive to K⁺ and Na⁺. Both the inhibition at pH 6.0 and the activation promoted by the polysaccharide were antagonized by monovalent cations (K⁺>Na⁺Li⁺).Abbreviations Mops 4-morpholinopropanesulfonic acid - EDTA ethylenediaminetetraacetic acid - ACMA 9-amino-6-chloro-2-methoxyacridine - FCCP carbonyl cyanide p(trifluoromethoxy)-phenylhyrazone     

Comparative Analysis of Short- and Long-Term Changes in Gene Expression Caused by Low Water Potential in Potato (Solanum tuberosum) Cell-Suspension Cultures

To dissect the cellular response to water stress and compare changes induced as a generalized response with those involved in tolerance/acclimation mechanisms, we analyzed changes in two-dimensional electrophoretic patterns of in vivo [35S]methionine-labeled polypeptides of cultured potato (Solanum tuberosum) cells after gradual and long exposure to polyethylene glycol (PEG)- mediated low water potential versus those induced in cells abruptly exposed to the same stress intensity. Protein synthesis was not inhibited by gradual stress imposition, and the expression of 17 proteins was induced in adapted cells. Some polypeptides were inducible under mild stress conditions (5% PEG) and accumulated further when cells were exposed to a higher stress intensity (10 and 20% PEG). The synthesis of another set of polypeptides was up-regulated only when more severe water-stress conditions were applied, suggesting that plant cells were able to monitor different levels of stress intensity and modulate gene expression accordingly. In contrast, in potato cells abruptly exposed to 20% PEG, protein synthesis was strongly inhibited. Nevertheless, a large set of polypeptides was identified whose expression was increased. Most of these polypeptides were not induced in adapted cells, but many of them were common to those observed in abscisic acid (ABA)-treated cells. These data, along with the finding that cellular ABA content increased in PEG-shocked cells but not in PEG-adapted cells, suggested that this hormone is mainly involved in the rapid response to stress rather than long-term adaptation. A further group of proteins included those induced after long exposure to both water stress and shock. Western blot analysis revealed that osmotin was one protein belonging to this common group. This class may represent induced proteins that accumulate specifically in response to low water potential and that are putatively involved in the maintenance of cellular homeostasis under prolonged stress.     

Big flies, small repeats: the "Thr-Gly" region of the period gene in Diptera

The region of the clock gene period (per) that encodes a repetitive tract of threonine-glycine (Thr-Gly) pairs has been compared between Dipteran species both within and outside the Drosophilidae. All the non- Drosophilidae sequences in this region are short and present a remarkably stable picture compared to the Drosophilidae, in which the region is much larger and extremely variable, both in size and composition. The accelerated evolution in the repetitive region of the Drosophilidae appears to be mainly due to an expansion of two ancestral repeats, one encoding a Thr-Gly dipeptide and the other a pentapeptide rich in serine, glycine, and asparagine or threonine. In some drosophilids the expansion involves a duplication of the pentapeptide sequence, but in Drosophila pseudoobscura both the dipeptide and the pentapeptide repeats are present in larger numbers. In the nondrosophilids, however, the pentapeptide sequence is represented by one copy and the dipeptide by two copies. These observations fulfill some of the predictions of recent theoretical models that have simulated the evolution of repetitive sequences.      

Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.      

Round-cell mutants of Salmonella typhimurium produced by transposition mutagenesis: Lethality of rodA and mre mutations

Summary Thirty-three insertions of transposon Tn10l6l7 into genes involved in the control of rod cell shape were isolated in Salmonella typhimurium by the characteristic glossy appearance of colonies composed of spherical cells. Genetic tests demonstrated that 25 (76%) were insertions in the rodA gene, 7 (21 %) were mre mutants, and 1 (3%) was a divD mutant. No insertion in the pbpA gene were found. Insertions in cell shape genes only appeared when strains displaying resistance to mecillinam (not caused by -lactamase production) were employed. Neither rodA nor mre insertions could be transduced to wild-type strains but they were normally accepted by mecillinam-resistant derivatives and by cya and crp mutants, which, unlike the corresponding Escherichia coli strains, did not display resistance to mecillinam. On the other hand, the divD insertion could be efficiently transduced to any strain. It is concluded that the rodA, mre, and divD genes are involved in the control of rod cell shape but, in addition, the RodA and Mre products perform some function(s) that is essential for wild-type cells but dispensable for some mecillinam-resistant strains, and for cya and crp mutants.     

Abscisic acid and mefluidide in the regulation of cold hardiness development in Solanum tuberosum L. potato

Plants of Solanum tuberosum L. potato do not cold acclimate when exposed to low temperature such as 5°C, day/night. When ABA (45 M) was added to the culture medium, stem-cultured plantlets of S. tuberosum, cv. Red Pontiac, either grown at 20°C/15°C, day/night, or at 5°C, increased in cold hardiness from –2°C (killing temperature) to –4.5°C. The increase in cold hardiness could be inhibited in both temperature regimes if cycloheximide (70 M) was added to the culture medium at the inception of ABA treatment. Cycloheximide did not inhibit cold hardiness development, however, when it was added to the culture medium 3 days after ABA treatment.When pot-grown plants were foliar sprayed with mefluidide (50 M), ABA content increased from 10 nmol to 30 nmol g^–1 dry weight and plants increased in cold hardiness from –2°C to about –3.5°C. The increases in free ABA and cold hardiness occurred only in plants grown at 20°C/15°C; neither ABA nor cold hardiness increased in plants grown at 5°C.The results suggest that an increase in ABA and a subsequent de novo synthesis of proteins are required for the development of cold hardiness in S. tuberosum regardless of temperature regime, and that the inability to synthesize ABA at low temperature, rather than protein synthesis, appears to be the reason why S. tuberosum does not cold acclimate.     

A scanning electron microscope study of normal and vitrified leaves from Datura insignis plantlets cultured in vitro

The surface anatomy of normal and vitreous leaves of plantlets obtained from Datura insignis Barb Rodr nodal segment cultures was compared using scanning electron microscopy. Normal and vitrified leaves are similar in several ways. They are both amphistomatic, and have similar distributions of glandular and non-glandular trichomes. Stomata have similar length, diameter and distribution in normal and vitreous plants. Immature stomata, which have closed pores, and plugged stomata, which contain an amorphous material between their guard cells, occur in both normal and vitrified leaves. Normal and vitreous leaves differ in the frequency of normal and abnormal stomata. Normal stomata have kidney-shaped guard cells and resemble closely those found in field-grown plants, whereas abnormal stomata have deformed guard cells. Normal stomata represent approximately 80% of the total number of stomata in normal leaves, but only 7% of the total number of stomata in vitreous leaves. Abnormal stomata represent 90% of the total number in vitreous leaves. The deformation of guard cells could possibly be a mechanical impediment to stomatal function.