A NEW,HETEROTHALLIC SPECIES OF SORDARIA

Olive , L. S., and A. A. Fantini . (Columbia U., New York, N. Y.) A new, heterothallic species of Sordaria. Amer. Jour. Bot. 48(2): 124–128. Illus. 1961.—S. brevicollis, sp. nov., was isolated from zebra dung from the New York Zoological Park. It is the only species of the genus that has been found to be heterothallic and to have microconidia. The latter function readily in fertilization. Heterothallism is controlled by a single allelic pair of compatibility factors located about 14.2 crossover units from the centromere. Incomplete mating reactions involving this species, Gelasinospora autosteira, and Neurospora crassa indicate relationships among these 3 genera.     

EPISTASIS BETWEEN NEW MUTATIONS AND GENETIC BACKGROUND AND A TEST OF GENETIC CANALIZATION

Abstract The importance for fitness of epistatic interactions among mutations is poorly known, yet epistasis can exert important effects on the dynamics of evolving populations. We showed previously that epistatic interactions are common between pairs of random insertion mutations in the bacterium Escherichia coli . In this paper, we examine interactions between these mutations and other mutations by transducing each of twelve insertion mutations into two genetic backgrounds, one ancestral and the other having evolved in, and adapted to, a defined laboratory environment for 10,000 generations. To assess the effect of the mutation on fitness, we allowed each mutant to compete against its unmutated counterpart in that same environment. Overall, there was a strong positive correlation between the mutational effects on the two genetic backgrounds. Nonetheless, three of the twelve mutations had significantly different effects on the two backgrounds, indicating epistasis. There was no significant tendency for the mutations to be less harmful on the derived background. Thus, there is no evidence supporting the hypothesis that the derived bacteria had adapted, in part, by becoming buffered against the harmful effects of mutations.     

阿魏侧耳一新变种及其培养特征

本文报道在新疆塔城和木垒地区采集到阿魏侧耳一新变种,命名为阿魏侧耳托里变种[Pleurotus eryngii(DC.ex Ft.)Quel.var.tuoliensis Mou n.var.],并附汉文和拉丁文描述。同时还讨论了新变种和阿魏侧耳之间的区别。     

SOME ASPECTS OF THE PHYSIOLOGY AND BIOCHEMISTRY OF MARINE FUNGI

1. This review deals with certain aspects of the physiology and biochemistry of marine fungi. Though it is not easy to define what is meant by a marine fungus, the information presented here relates to those species that by consensus can be accepted as being truly marine. The material is in two parts, that relating to the higher fungi (Ascomycotina, Basidiomycotina and Deuteromycotina) and that relating to the lower fungi, particularly those zoosporic fungi that require sodium for growth. 2. Higher marine fungi appear to have a similar carbon, nitrogen and vitamin nutrition to their terrestrial counterparts. 3. Growth of higher marine fungi can be optimal in 100% sea water, but more frequently optimal growth is at a lower percentage. The percentage giving optimal growth may be determined by the rate of ion uptake required to generate the necessary turgor for growth. The tolerance of the vegetative phase of many terrestrial fungi to salinity appears little different from that of marine fungi. In general, members of the Basidiomycotina are particularly sensitive to salinity, while those of the Ascomycotina and Deuteromycotina are much more tolerant. 4. The degree of tolerance to salinity may be dependent upon temperature and whether or not adaptation by the fungus has occurred. 5. Maintenance of a suitable internal potassium concentration by a higher marine fungus is important for growth in a saline medium. Calcium appears to be necessary for the retention of potassium and organic solutes within the hyphae. 6. It appears that higher marine fungi are able to maintain a ratio of potassium: sodium higher than that of sea water by the presence of a plasma membrane ATPase which may have a higher pH optimum than the equivalent enzyme from terrestrial counterparts. 7. Higher fungi produce more glycerol as the salinity of the external medium is increased. Whether or not the compound is involved in osmoregulation has yet to be determined. 8. Turgor is thought to be generated in higher marine fungi growing in sea water by organic solutes (predominantly glycerol and arabitol) and by ions, with the latter playing the major role. Though interpretation of the data depends on several assumptions, the high concentrations of sodium that seem likely to be present in hyphae or cells have implications for the activity of enzymes, if they have similar properties to those of higher plants. There is a need for information on the effects of high concentrations of ions on enzymes located in the cytoplasm of higher fungi. 9. In spite of some experimental uncertainties, it seems that reproduction and spore germination of higher marine fungi are very much less affected by salinity than are the same processes of terrestrial counterparts. 10. The zoosporic marine fungi require sodium for growth. Though the ion is required at high concentration for growth, sodium cannot be replaced by potassium. Evidence indicates that sodium is involved in the transport of solutes across the plasma membrane. 11. The carbon and nitrogen requirements for the growth of the zoosporic marine fungi demand further investigation, particularly at the biochemical level. There is evidence that the respiration of these fungi possesses many interesting features. 12. Vitamin requirements of the zoosporic marine fungi depend on the isolate under investigation. Vitamin B., does not now seem to be an obligatory requirement. The ability of phospholipids and sterols to stimulate growth requires further investigation. 13. Further studies on marine fungi in the laboratory should focus particularly on growth in continuous culture. Physiological and biochemical studies would be helped by more precise guidance from those concerned with the ecology of these fungi.     

SOME ASPECTS OF BIOELECTRICAL PHENOMENA

It is pointed out that there are great advantages in using single cells instead of tissues in the study of bioelectrical phenomena. Certain bioelectrical phenomena are discussed in relation to the structure of protoplasm. Under certain circumstances measurements of potential differences may enable us to determine what ions enter the protoplasm. Under suitable conditions we are able to ascertain the potential differences across the protoplasm at single points, instead of being obliged merely to measure the differences between two points.