Bacterial species and evolution: Theoretical and practical perspectives

A discussion of the species problem in modern evolutionary biology serves as the point of departure for an exploration of how the basic science aspects of this problem relate to efforts to map bacterial diversity for practical pursuits—for prospecting among the bacteria for useful genes and gene-products. Out of a confusing array of species concepts, the Cohesion Species Concept seems the most appropriate and useful for analyzing bacterial diversity. Techniques of allozyme analysis and DNA fingerprinting can be used to put this concept into practice to map bacterial genetic diversity, though the concept requires minor modification to encompass cases of complete asexuality. Examples from studies of phenetically definedBacillus species provide very partial maps of genetic population structure. A major conclusion is that such maps frequently reveal deep genetic subdivision within the phenetically defined specles; divisions that in some cases are clearly distinct genetic species. Knowledge of such subdivisions is bound to make prospecting within bacterial diversity more effective. Under the general concept of genetic cohesion a hypothetical framework for thinking about the full range of species conditions that might exist among bacteria is developed and the consequences of each such model for species delineation, and species identification are discussed. Modes of bacterial evolution, and a theory of bacterial speciation with and without genetic recombination, are examined. The essay concludes with thoughts about prospects for very extensive mapping of bacterial diversity in the service of future efforts to find useful products. In this context, evolutionary biology becomes the handmaiden of important industrial activities. A few examples of past success in commercializing bacterial gene-products from species ofBacillus and a few other bacteria are reviewed.     

Arterial branching in man and monkey

Vessel diameters and branching angles are measured from a large number of arterial bifurcations in the retina of a normal human subject and in that of a rhesus monkey. The results are compared with each other and with theoretical results on this subject.     

Interaction of ouabain with the Na(+) pump in intact epithelial cells

To determine the specificity and efficacy of [(3)H]ouabain binding as a quantitative measure of the Na(+) pump (Na(+), K(+)-ATPase) and as a marker for the localization of pumps involved in transepithelial Na(+)-transport, we analyzed the interaction of [(3)H]ouabain with its receptor in pig kidney epithelial (LLC-PK(1)) cells. When these epithelial cells are depleted of Na(+) and exposed to 2 muM [(3)H]ouabain in a Na(+)-free medium, binding is reduced by 90 percent. When depleted of K(+) and incubated in a K(+)- free medium, the ouabain binding rate is increase compared with that measured at 5 mM. This increase is only demonstable when Na(+) is present. The increased rate could be attributed to the predominance of the Na(+)-stimulated phosphorylated form of the pump, as K(+) is not readily available to stimulate dephosphorylation. However, some binding in the K(+)-free medium is attributable to pump turnover (and therefore, recycling of K(+)), because analysis of K(+)-washout kinetics demonstrated that addition of 2 muM ouabain to K(+)-depleted cells increased the rate of K(+) loss. These results indicate that in intact epithelial cells, unlike isolated membrane preparations, the most favorable condition for supporting ouabain binding occurs when the Na(+), K(+)-ATPase is operating in the Na(+)-pump mode or is phosphorylated in the presence of Na(+). When LLC-PK(1) cells were exposed to ouabain at 4 degrees C, binding was reduced by 97 percent. Upon rewarming, the rate of binding was greater than that obtained on cells kept at a constant 37 degrees C. However, even at this accelerated rate, the time to reach equilibrium was beyond what is required for cells, swollen by exposure to cold, to recover normal volume. Thus, results from studies that have attempted to use ouabain to eliminate the contribution of the conventional Na(+) pump to volume recovery must be reevaluated if the exposure to ouabain was done in the cold or under conditions in which the Na(+) pump is not operating.     

X-ray microanalytical (EDX) investigation of potassium distributions in mesophyll cells of non-acclimated and cold-acclimated rye leaves

Electron probe X-ray microanalysis was used to analyse the effects of sub-zero temperatures on K⁺ distribution in compartments within non-acclimated and cold acclimated rye (Secale cereale L. cv Voima) leaf cells and to evaluate membrane leakage of ions caused by freezing-injury. The specimens were rapidly frozen from growing temperatures and from two different sub-zero temperatures (LT₅₀ and LT₁₀₀) to which the leaves had already been slowly cooled. Measurements were made in the cytoplasm, vacuole and cell walls in freeze-substituted mesophyll cells. At ambient temperatures, the mean K⁺ concentration in the cytoplasm (100 mol m^?3) differed significantly from that of the vacuole (49 mol m^?3) in the non-acclimated (NA) cells, while in cold acclimated (A) cells, the concentrations were similar (109 vs 93 mol m^?3, respectively). At LT₅₀ temperatures, the K⁺ concentration in NA-cells decreased significantly in the cytoplasm (59 mol m^?3) but increased in the cell walls. In the A-cells, on the other hand, the mean K⁺ concentration increased significantly (about three-fold) in all major compartments. At LT₁₀₀ temperatures, K⁺ concentrations in the cytoplasm and cell walls decreased when compared with corresponding LT₅₀ values in the A-cells but increased in the NA-cells. The increased potassium concentration in the cytoplasm of A-cells at LT₅₀ temperature is compatible with the observed cell shrinkage and an absence of plasma membrane damage. The decreased potassium concentration in the cytoplasm of NA-cells at LT₅₀ temperature is compatible with the slight cell shrinkage and suggests that the plasma membrane in these cells shows increased permeability due to freeze injury.     

The Seronera bull problem: The elephants

(1) The activities of bull elephants in the vicinity of the Serengeti National Park headquarters at Seronera was monitored from 1968 to 1971. (2) Elephant bulls congregate in small groups of ever–changing composition; a dominance heirarchy cuts across group integrity. (3) Occupancy of the drainage area of the Seronera river is predictable by rainfall; changes in occupancy level are a question of duration rather than amplitude. (4) The feeding behaviour of the bulls is described. It is argued that large Acacia trees are uprooted for nutritional rather than social reasons. The effects of the bulls on the Seronera woodlands will be analysed in Part II (Croze, 1974).     

Isolation and Hybridization Kinetics of Messenger RNA from <Emphasis Type="Italic">Dictyostelium discoideum</Emphasis>

Messenger RNA from the cellular slime mould Dictyostelium discoideum contains a sequence of poly A residues and more than 95% hybridizes to the non-reiterated DNA.     

Circulatory Adaptations of Snakes to Gravity

Comparative investigations of diverse taxa of snakes demonstratenumerous adaptations for counteracting effects of gravity onthe circulation, including morphological, physiological andbehavioral specializations. Arboreal and terrestrial snakesthat are normally subjected to stresses from gravity are characterizedby relatively high arterial pressures and ability to regulatepressure by physiological adjustments of flow and flow resistance.The heart occupies an anterior position, and the arterial bloodcolumn between the heart and head is comparatively short. Terrestrialsnakes characteristically possess short vascular lungs whicheliminate risks of pulmonary edema due to gravity effects duringvertical posture. Problems of blood pooling in peripheral systemicvasculature are counteracted by relatively non-compliant bodytissue, vasomotor adjustments, and specific movements that facilitatethe venous cardiac return. Anatomical valves appear to be absentfrom major venous channels, but gravity, acting in concert withspecificfeatures of venous morphology, can create valving actions thatimpede shifts of blood volume to dependent segments of thesevessels. Nearly all of these characteristics are absent or deficientin several independent lineages of aquatic snakes that are farless subject to gravitational disturbance of hydrostatic pressures.Thus, snakes provide diverse and particularly useful modelsfor examining cardiovascular adaptations to gravity, includingmechanisms of function and the evolution of cardiovascular design.     

Mechanism of paraquat tolerance in perennial ryegrass

Abstract The mechanism of paraquat tolerance was investigated in lines of perennial ryegrass (Lolium perenne L.) which had been selected for resistance to the herbicide. Uptake, metabolism and translocation of paraquat were studied. Susceptible cultivars and a tolerant line were not found to differ in uptake of radioactive paraquat applied to the leaf surface or supplied to the cut ends of excised leaves. Distribution of herbicide within leaf tissue was similar in tolerant and susceptible plants and no metabolites of ¹⁴C-paraquat were detected in tolerant or susceptible plants treated with sub-lethal concentrations of the herbicide. Autoradiography and quantitative determinations showed much variation in translocation of ¹⁴C-paraquat out of treated leaves of intact plants, but the variation was not related to the degree of susceptibility to the herbicide. It is concluded that paraquat tolerance in perennial ryegrass is unlikely to depend upon reduced uptake, enhanced metabolism or altered translocation of the herbicide.     

Studies on the mechanism for entry of vesicular stomatitis virus glycoprotein g mRNA into membrane-bound polyribosome complexes

Glycoprotein mRNA (G mRNA) of vesicular stomatitis virus is synthesized in the cytosol fraction of infected HeLa cells. Shortly after synthesis, this mRNA associates with 40S ribosomal subunits and subsequently forms 80S monosomes in the cytosol fraction. The bulk of labeled G mRNA is then found in polysomes associated with the membrane, without first appearing in the subunit or monomer pool of the membrane-bound fraction. Inhibition of the initiation of protein synthesis by pactamycin or muconomycin A blocks entry of newly synthesized G m RNA into membrane-bound polysomes. Under these circumstances, labeled G mRNA accumulates into the cytosol. Inhibition of the elongation of protein synthesis by cucloheximide, however, allows entry of 60 percent of newly synthesized G mRNA into membrane-bound polysomes. Furthermore, prelabeled G mRNA associated with membrane-bound polysomes is released from the membrane fraction in vivo by pactamycin or mucomycon A and in vitro by 1mM puromycin - 0.5 M KCI. This release is not due to nonspecific effects of the drugs. These results demonstrate that association of G mRNA with membrane-bound polysomes is dependent upon polysome formation and initiation of protein synthesis. Therefore, direct association of the 3' end of G mRNA with the membrane does not appear to be the initial event in the formation of membrane-bound polysomes.     

MMP-9, TIMP-1 and inflammatory cells in sputum from COPD patients during exacerbation

Background

Irreversible airflow obstruction in Chronic Obstructive Pulmonary Disease (COPD) is thought to result from airway remodelling associated with aberrant inflammation. Patients who experience frequent episodes of acute deterioration in symptoms and lung function, termed exacerbations, experience a faster decline in their lung function, and thus over time greater disease severity However the mechanisms by which these episodes may contribute to decreased lung function are poorly understood.This study has prospectively examined changes in sputum levels of inflammatory cells, MMP-9 and TIMP-1 during exacerbations comparing with paired samples taken prior to exacerbation.

Methods

Nineteen COPD patients ((median, [IQR]) age 69 [63 to 74], forced expiratory volume in one second (FEV1) 1.0 [0.9 to1.2], FEV1% predicted 37.6 [27.3 to 46.2]) provided sputa at exacerbation. Of these, 12 were paired with a samples collected when the patient was stable, a median 4 months [2 to 8 months] beforehand.

Results

MMP-9 levels increased from 10.5 μg/g [1.2 to 21.1] prior to exacerbation to 17.1 μg/g [9.3 to 48.7] during exacerbation (P < 0.01). TIMP-1 levels decreased from 3.5 μg/g [0.6 to 7.8] to 1.5 μg/g [0.3 to 4.9] (P = 0.16). MMP-9/TIMP-1 Molar ratio significantly increased from 0.6 [0.2 to 1.1] to 3.6 [2.0 to 25.3] (P < 0.05). Neutrophil, eosinophil and lymphocyte counts all showed significant increase during exacerbation compared to before (P < 0.05). Macrophage numbers remained level. MMP-9 levels during exacerbation showed highly significant correlation with both neutrophil and lymphocyte counts (Rho = 0.7, P < 0.01).

Conclusion

During exacerbation, increased inflammatory burden coincides with an imbalance of the proteinase MMP-9 and its cognate inhibitor TIMP-1. This may suggest a pathway connecting frequent exacerbations with lung function decline.