Protists have divergent effects on bacterial diversity along a productivity gradient

Productivity and predation are thought to be crucial drivers of bacterial diversity. We tested how the productivity–diversity of a natural bacterial community is modified by the presence of protist predators with different feeding preferences. In the absence of predators, there was a unimodal relationship between bacterial diversity and productivity. We found that three protist species (Bodo, Spumella and Cyclidium) had widely divergent effects on bacterial diversity across the productivity gradient. Bodo and Cyclidium had little effect on the shape of the productivity–diversity gradient, while Spumella flattened the relationship. We explain these results in terms of the feeding preferences of these predators.     

Cilia in the fetal and neonatal canine retina

Cilia in the canine retina were examined at 40, 46 and 50 days of gestation and at birth by scanning electron microscopy, transmission electron microscopy, and by the freeze-fracture technique. Cilia were similar in all age groups examined. Scanning electron micrographs showed them to be smooth-surfaced conical to tubular extensions arising from putative photoreceptor inner segments. Cilia when freeze-fractured contained variable numbers of circumferential rows of 10 nm P-face particles: these constitute the ciliary necklace. Transmission electron micrographs showed the ciliary membrane to contain electron-dense beads which corresponded to the ciliary necklace seen in freeze-fracture replicas. The ciliary necklace identified in the developing canine retina was similar to those found in other types of motile and sensory cilia.     

The phylogeny of the hominoid primates: a statistical analysis of the DNA-DNA hybridization data

Sibley and Ahlquist compared the single-copy nuclear DNA sequences of the hominoid primates using DNA-DNA hybridization. From this data set they estimated a phylogeny that clusters man and chimpanzees using a distance Wagner procedure. However, no assessment of statistical confidence in this estimated phylogeny was made, despite the fact that their data set contains internal inconsistencies concerning the correct branching order. This paper presents a modification of Pielou's Q- statistic that allows one to make nonparametric tests of phylogenetic relationship from distance data. The results of this analysis indicate that the estimated phylogeny of Sibley and Ahlquist is without statistical significance owing to the internal inconsistencies of the data set. A survey and additional analyses of other types of molecular data indicate that the phylogeny that clusters chimpanzees and gorillas and has the human lineage splitting off earlier is statistically consistent with all the molecular data (including the DNA-DNA hybridization data), whereas the phylogeny estimated by Sibley and Ahlquist can be rejected at the 5% level using the data on restriction- endonuclease sites in the mitochondrial genome.      

Nuclear Fraction of Bacillus subtilis as a Template for Ribonucleic Acid Synthesis

A "nuclear fraction" prepared from Bacillus subtilis was a more efficient template than purified deoxyribonucleic acid for the synthesis of ribonucleic acid by exogenously added ribonucleic acid polymerase isolated from B. subtilis. The initial rate of synthesis with the nuclear fraction was higher and synthesis continued for several hours, yielding an amount of ribonucleic acid greater than the amount of deoxyribonucleic acid used as the template. The product was heterogenous in size, with a large portion exceeding 23S. When purified deoxyribonucleic acid was the template, a more limited synthesis was observed with a predominantly 7S product. However, the ribonucleic acids produced in vitro from these templates were very similar to each other and to in vivo synthesized ribonucleic acid as determined by the competition of ribonucleic acid from whole cells in the annealing of in vitro synthesized ribonucleic acids to deoxyribonucleic acid. Treatment of the nuclear fraction with heat (60 C for 15 min) or trypsin reduced the capacity of the nuclear fraction to synthesize ribonucleic acid to the level observed with purified deoxyribonucleic acid.     

Interactions ofCandida albicans with bacteria and salivary molecules in oral biofilms

The yeastCandida albicans coaggregates with a variety of streptococcal species, an interaction that may promote oral colonization by yeast cells.C. albicans andCandida tropicalis are the yeasts most frequently isolated from the human oral cavity and our data demonstrate that both these species bind toStreptococcus gordonii NCTC 7869 while two otherCandida species (Candida krusei andCandida kefyr) do not. Adherence ofC. albicans was greatest when the yeast had been grown at 30° C to mid-exponential growth phase. For 21 strains ofC. albicans there was a positive correlation between the ability to adhere toS. gordonii and adherence to experimental salivary pellicle. Whole saliva either stimulated or slightly inhibited adherence ofC. albicans toS. gordonii depending on the streptococcal growth conditions. The results suggest that the major salivary adhesins and coaggregation adhesins ofC. albicans are co-expressed.     

Translation of RNAs Synthesized In Vivo and In Vitro from Bacteriophage SP82 DNA

The synthesis of 69 phage-specific polypeptides during the infection of Bacillus subtilis with bacteriophage SP82 was detected by pulse-labeling, one-dimensional electrophoresis, and autoradiography. SP82 virions were found to contain approximately 22 polypeptides, most of which were synthesized late in infection; evidence was obtained for the processing of the major virion protein. RNAs extracted at different times during infection were translated by using an Escherichia coli cell-free extract. Only smaller-molecular-weight peptides were produced efficiently in vitro; in the 9,000- to 60,000-molecular-weight range, 50 to 60% of the peptides synthesized in vivo were produced by translation of RNAs extracted from infected cells. Eight of the virion peptides were produced by in vitro translation of RNAs extracted from infected cells. RNAs were synthesized under defined conditions by RNA polymerase extracted from uninfected B. subtilis and by polymerases isolated from cells 8 and 20 min after infection with SP82. Translation of these RNAs yielded characteristic and different patterns of polypeptides. Nine of the 12 polypeptides produced by translation of RNAs synthesized by the host polymerase corresponded in mobility to peptides appearing in vivo in the 0 to 3 and 3 to 6 min intervals of pulse-labeling after infection; 12 of the 25 peptides synthesized from RNAs produced by polymerase extracted 8 min after infection corresponded in mobility to peptides detected in vivo 8 min after infection, and 15 of the 22 peptides directed by RNAs made by the polymerase isolated 20 min after infection corresponded to peptides present in vivo late in infection. Five of the peptides produced in vitro from the latter RNA corresponded to virion peptides.     

Cyclic hydrolase-transfected 3T3 cells have low levels of inositol 1,2-cyclic phosphate and reach confluence at low density.

The cDNA that encodes inositol-1,2-cyclic phosphate 2-phosphohydrolase (cyclic hydrolase), an enzyme that converts inositol 1,2-cyclic phosphate (cIns(1,2)P) to inositol 1-phosphate, was expressed in 3T3 cells to investigate the function of inositol cyclic phosphates. Cells with increased cyclic hydrolase activity had lower levels of cIns(1,2)P and grew to a lower density at confluence than control cells. This relationship was strengthened by the demonstration that several cell types with differences in cyclic hydrolase activity had levels of cIns(1,2)P and saturation densities that also correlated inversely with cyclic hydrolase activity. In addition, cyclic hydrolase activity is higher in cells at confluence compared to subconfluence. These results suggest that cellular cIns(1,2)P levels are determined by cyclic hydrolase activity and play a role in the control of cell proliferation.