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481.
Florian Weinberger Hans-Georg Hoppe Michael Friedlander 《Journal of applied phycology》1997,9(3):277-285
Of 45 bacterial isolates from healthy tips of Gracilaria conferta (Schousboe ex Montagne) J. et G. Feldmann, 29% were identified
as ‘conditional inducers’ of an apical necrosis. That is, the isolates induced necrotic tips in G. conferta within 16 h after
elimination of most of the resident microflora from the alga. Several disinfectants and antibiotics were screened for their
ability to induce algal susceptibility to the bacteria and to suppress uncontrolled appearance of tip necrosis. Treatment
with 100 mg L-1 Cefotaxim + 100 mg L-1Vancomycin over three days was the least damaging and most efficient. Tip necrosis was related to isolates of the Corynebacterium-Arthrobacter-group
and to the Flavobacterium-Cytophaga-group. The damaging effect occurred due to the bacterial excretion of active agents and
was not correlated with acapability to degrade agar. The damaging influence of four Cytophaga-likestrains was inhibited by
20 of 40 isolates. This protective effect was caused by very different organisms. In five of six cases examined further, the
effect was not cellbound, but due to the excretion of agents. These were not antimicrobially active, but inactivated necrosis-inducing
excretions. These results indicate that epiphytic bacterial degradation or inactivation of damaging agents is a protecting
factor in Gracilaria, which prevents the alga from being harmed by epiphytes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
482.
Samer Halabi Michael Ghosh Stefan Stevanovi Hans-Georg Rammensee Luca D. Bertzbach Benedikt B. Kaufer Martin C. Moncrieffe Bernd Kaspers Sonja Hrtle Jim Kaufman 《PLoS biology》2021,19(4)
Viral diseases pose major threats to humans and other animals, including the billions of chickens that are an important food source as well as a public health concern due to zoonotic pathogens. Unlike humans and other typical mammals, the major histocompatibility complex (MHC) of chickens can confer decisive resistance or susceptibility to many viral diseases. An iconic example is Marek’s disease, caused by an oncogenic herpesvirus with over 100 genes. Classical MHC class I and class II molecules present antigenic peptides to T lymphocytes, and it has been hard to understand how such MHC molecules could be involved in susceptibility to Marek’s disease, given the potential number of peptides from over 100 genes. We used a new in vitro infection system and immunopeptidomics to determine peptide motifs for the 2 class II molecules expressed by the MHC haplotype B2, which is known to confer resistance to Marek’s disease. Surprisingly, we found that the vast majority of viral peptide epitopes presented by chicken class II molecules arise from only 4 viral genes, nearly all having the peptide motif for BL2*02, the dominantly expressed class II molecule in chickens. We expressed BL2*02 linked to several Marek’s disease virus (MDV) peptides and determined one X-ray crystal structure, showing how a single small amino acid in the binding site causes a crinkle in the peptide, leading to a core binding peptide of 10 amino acids, compared to the 9 amino acids in all other reported class II molecules. The limited number of potential T cell epitopes from such a complex virus can explain the differential MHC-determined resistance to MDV, but raises questions of mechanism and opportunities for vaccine targets in this important food species, as well as providing a basis for understanding class II molecules in other species including humans.This study shows that chicken MHC class II molecules present peptides from only a handful of the more than 100 genes of the oncogenic herpesvirus Marek’s disease virus, explaining the strong genetic association of chicken MHC with resistance and susceptibility to this and other economically-important pathogens. 相似文献
483.
Summary The chloroplast DNAs of Acetabularia mediterranea strains 5 and 17 differ significantly in their restriction patterns. Southern blotting analysis using gene probes derived from the coding regions of spinach genes showed that psbB and petB each map to unique restriction fragments which are shared in strains 5 and 17. On the other hand psaA, psbA and rbcL map to different restriction fragments in strains 5 and 17 probably as a result of restriction fragment length polymorphism. In addition to restriction fragment polymorphism there is evidence for much larger differences in the organization of the plastome. The most striking difference is the absence in strain 5 of a 10 kb repeated sequence which has previously been demonstrated in strain 17. However, both strains apparently share at least 8 kb of the 10 kb repeated sequence. Restriction analysis of independent clones of the 10 kb sequence revealed a family of non-identical repeats.This paper is dedicated to the memory of Prof. H.G. Schweiger, Director of the Max-Planck-Institut fur Zellbiologie, who died in November 1986Deceased 相似文献
484.
Ralph Jack Gabriele Bierbaum Christoph Heidrich Hans-Georg Sahl 《BioEssays : news and reviews in molecular, cellular and developmental biology》1995,17(9):793-802
The lantibiotics are a rapidly expanding group of biologically active peptides produced by a variety of Gram-positive bacteria, and are so-called because of their content of the thioether amino acids lanthionine and β-methyllanthionine. These amino acids, and indeed a number of other unusual amino acids found in the lantibiotics, arise following post-translational modification of a ribosomally synthesised precursor peptide. A number of genes involved in the biosynthesis of these highly modified peptides have been identified, including genes encoding the precursor peptide, enzymes responsible for specific amino acid modifications, proteases able to remove the leader peptide, ABC-superfamily transport proteins involved in lantibiotic translocation, regulatory proteins controlling lantibiotic biosynthesis and proteins that protect the producing strain from the action of its own lantibiotic. Analysis of these genes and their products is allowing greater understanding of the complex mechanism(s) of the biosynthesis of these unique peptides. 相似文献