Ascospore septation inDiploschistes (Thelotremataceae, lichenizedAscomycota) and the taxonomic significance of macro- and microcephalic ascospore types

The ascospore septation in 13 species ofDiploschistes was examined. Microcephalic, macrocephalic, as well as irregular ascospore septation were found. In some species and even specimens of some species, different types of spore septation were detected. The taxonomic significance of the character of ascospore septation sequence is questioned, and the distinction of the ordersGraphidales andOstropales, which was primarily based on this character, is rejected.This paper is dedicated to Prof. DrRolf Santesson (Uppsala) on the occasion of his 80th birthday.     

Fluorescence techniques in biotechnology

The high specificity and sensitivity of fluorescence techniques have made them important analytical tools in medicine and biotechnology. Besides monitoring and quantitative detection of biomolecules these methods can be used for controlling bacterial activities or for measuring physiological states of cells or tissues. Three topics of importance in biotechnology — immunoassays, photosynthesis and fermentation — are treated in detail.     

The effect of penicillin on competence in Bacillus subtilis cultures growing in chemostat at different doubling times

Summary The relationships between penicillin-resistance and competence at different doubling-times have been studied in a chemostat. Both subinhibitory and lethal levels of drug have a differential effect on competent fraction and cell viability. Transformation frequency was rather increased in the presence of inhibitory doses of penicillin when partially affected cells were protected from lysis by using an isotonic medium; however, transformation frequency decreases when protoplasts were detected.The influence of the doubling-time in the ability of the recipient population to undergo transformation was confirmed. Our results, in accordance with that previously found, might suggest that competence in log phase and competence in the stationary phase could differ in some important aspects.     

Exotic fish species in a global biodiversity hotspot: observations from River Chalakudy,part of Western Ghats,Kerala, India

We record here the occurrence of five exotic fish species viz Oreochromis mossambicus, Gambusia affinis, Osphronemus goramy, Xiphophorus maculatus and Poecilia reticulata in the Chalakudy River, part of the Western Ghats, a global biodiversity hotspot in Kerala, India. O. mossambicus was ubiquitous in occurrence with large shoals being encountered at all sampling sites spread along the downstream-upstream gradient of the river, including at an altitude of 1050 m ASL. Osphronemus goramy was recorded from the downstream region of the river while Gambusia affinis was recorded from three sampling sites located downstream as well as midstream. Xiphophorus maculatus was collected from a second order stream flowing through a tea plantation at an altitude of 1050 m ASL. Samples of brooders and early fry of Poecilia reticulata indicate that the fish has already established a breeding population in the river. Possible threats to the indigenous fish fauna of the Chalakudy River as a result of the invasion and proliferation of these exotics is discussed.     

Does intra-individual major histocompatibility complex diversity keep a golden mean?

An adaptive immune response is usually initiated only if a major histocompatibility complex (MHC) molecule presents pathogen-derived peptides to T-cells. Every MHC molecule can present only peptides that match its peptide-binding groove. Thus, it seems advantageous for an individual to express many different MHC molecules to be able to resist many different pathogens. However, although MHC genes are the most polymorphic genes of vertebrates, each individual has only a very small subset of the diversity at the population level. This is an evolutionary paradox. We provide an overview of the current data on infection studies and mate-choice experiments and conclude that overall evidence suggests that intermediate intra-individual MHC diversity is optimal. Selective forces that may set an upper limit to intra-individual MHC diversity are discussed. An updated mathematical model based on recent findings on T-cell selection can predict the natural range of intra-individual MHC diversity. Thus, the aim of our review is to evaluate whether the number of MHC alleles usually present in individuals may be optimal to balance the advantages of presenting an increased range of peptides versus the disadvantages of an increased loss of T-cells.