抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Antibiotics have always been considered one of the wonder discoveries of the 20th century. This is true, but the real wonder is the rise of antibiotic resistance in hospitals, communities, and the environment concomitant with their use. The extraordinary genetic capacities of microbes have benefitted from man's overuse of antibiotics to exploit every source of resistance genes and every means of horizontal gene transmission to develop multiple mechanisms of resistance for each and every antibiotic introduced into practice clinically, agriculturally, or otherwise. This review presents the salient aspects of antibiotic resistance development over the past half-century, with the oft-restated conclusion that it is time to act. To achieve complete restitution of therapeutic applications of antibiotics, there is a need for more information on the role of environmental microbiomes in the rise of antibiotic resistance. In particular, creative approaches to the discovery of novel antibiotics and their expedited and controlled introduction to therapy are obligatory.

Origins and Evolution of Antibiotic Resistance

The optimism of the early period of antimicrobial discovery has been tempered by the emergence of bacterial strains with resistance to these therapeutics. Today, clinically important bacteria are characterized not only by single drug resistance but also by multiple antibiotic resistance--the legacy of past decades of antimicrobial use and misuse. Drug resistance presents an ever-increasing global public health threat that involves all major microbial pathogens and antimicrobial drugs.

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Antibacterial resistance worldwide: causes, challenges and responses.

Purification and properties of unicellular blue-green algae (order Chroococcales).

Microbial pathogenesis in cystic fibrosis: mucoid Pseudomonas aeruginosa and Burkholderia cepacia.

Endophytic bacteria reside within plant hosts without causing disease symptoms. In this study, 853 endophytic strains were isolated from aerial tissues of four agronomic crop species and 27 prairie plant species. We determined several phenotypic properties and found approximately equal numbers of gram-negative and gram-positive isolates. In a greenhouse study, 28 of 86 prairie plant endophytes were found to colonize their original hosts at 42 days postinoculation at levels of 3.5 to 7.7 log(10) CFU/g (fresh weight). More comprehensive colonization studies were conducted with 373 corn and sorghum endophytes. In growth room studies, none of the isolates displayed pathogenicity, and 69 of the strains were recovered from corn or sorghum seedlings at levels of 8.3 log(10) CFU/plant or higher. Host range greenhouse studies demonstrated that 26 of 29 endophytes were recoverable from at least one host other than corn and sorghum at levels of up to 5.8 log(10) CFU/g (fresh weight). Long-range dent corn greenhouse studies and field trials with 17 wild-type strains and 14 antibiotic-resistant mutants demonstrated bacterial persistence at significant average colonization levels ranging between 3.4 and 6.1 log(10) CFU/g (fresh weight) up to 78 days postinoculation. Three prairie and three agronomic endophytes exhibiting the most promising levels of colonization and an ability to persist were identified as Cellulomonas, Clavibacter, Curtobacterium, and Microbacterium isolates by 16S rRNA gene sequence, fatty acid, and carbon source utilization analyses. This study defines for the first time the endophytic nature of Microbacterium testaceum. These microorganisms may be useful for biocontrol and other applications.

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Isolation and Characterization of Endophytic Colonizing Bacteria from Agronomic Crops and Prairie Plants

The purification and properties of a lipid-containing bacteriophage, phi6, are described. The phage contains a lipid envelope which is probably essential for infection. Infectivity of phi6 was lost in the presence of organic solvents, sodium deoxycholate, and phospholipase A. The fatty acid composition of the phage lipid was similar to that of the Pseudomonas phaseolicola host cells. The phage was composed of about 25% lipid, 13% RNA, and 62% protein. The buoyant density of phi6 was 1.27 g/ml in cesium chloride. The morphology of phi6 was unusual; it had a polyhedral head of about 60 nm surrounded by a membranous, compressible envelope which appeared to assume an elongated configuration upon attachment to pili. The adsorption rate constant was 3.3 x 10(-10) ml/min in a semi-synthetic medium and 3.8 x 10(-10) ml/min in a nutrient broth-yeast extract medium. The latent period was shorter in the former medium (80-115 min compared with 120-160 min), and the average burst size was larger (250-400 compared with 125-150). The eclipse period coincided with the latent period.

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Bacteriophage φ6: a Lipid-Containing Virus of Pseudomonas phaseolicola

A total of 23 strains of coryneform bacteria that cause ratoon stunting disease of sugarcane and Bermudagrass stunting disease were examined. These included 17 sugarcane strains from Florida, Louisiana, South Africa, Brazil, and Japan and six Bermudagrass strains from Florida and Taiwan. The sugarcane and Bermudagrass strains contained 2,4-diaminobutyric acid, rhamnose, and fucose in their cell walls, suggesting a relationship to some other phytopathogenic coryneform bacteria and related organisms with similar cell wall compositions. The cellular protein patterns of the sugarcane and Bermudagrass strains after polyacrylamide gel electrophoresis resembled the patterns of Corynebacterium michiganense subspecies more than the patterns of some other diaminobutyric acid-containing taxa. The protein patterns of the sugarcane strains were distinct from the patterns of the Bermudagrass strains examined. The guanine-plus-cytosine contents of the deoxyribonucleic acids of two sugarcane strains and one Bermudagrass strain were 66 mol%. The sugarcane and Bermudagrass strains formed a homogeneous group based on morphological characteristics and most biochemical characteristics. All of the sugarcane strains were nonpigmented (white) and grew more slowly in culture than the yellow-pigmented Bermudagrass strains. The Bermudagrass strains, unlike the sugarcane strains, hydrolyzed starch and utilized citrate and malate. Although the phytopathogenic coryneform bacteria with 2,4-diaminobutyric acid in the peptidoglycans of their cell walls are presently classified in the genus Corynebacterium, recent studies have indicated that these phytopathogens should be reclassified. These bacteria form a distinct group with characteristics different from those of all existing genera as presently circumscribed; therefore, we propose that a new genus, Clavibacter, be established for these and similar bacteria. We propose reclassification of Corynebacterium michiganense (including Corynebacterium michiganense subsp. michiganense, Corynebacterium michiganense subsp. insidiosum, Corynebacterium michiganense subsp. sepedonicum, Corynebacterium michiganense subsp. nebraskense, and Corynebacterium michiganense subsp. tessellarius), Corynebacterium iranicum, Corynebacterium tritici, and Corynebacterium rathayi in the new genus Clavibacter. We further propose that Clavibacter xyli be recognized as a new species with the following subspecies: Clavibacter xyli subsp. xyli sp. nov., subsp. nov., the species and subspecies type strain of which is sugarcane strain L1A (= ATCC 33974 = NCPPB 3152 = PDDC 7127), and Clavibacter xyli subsp. cynodontis subsp. nov., the subspecies type strain of which is Bermudagrass strain TB1A (= ATCC 33973).

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Clavibacter: a New Genus Containing Some Phytopathogenic Coryneform Bacteria, Including Clavibacter xyli subsp. xyli sp. nov., subsp. nov. and Clavibacter xyli subsp. cynodontis subsp. nov., Pathogens That Cause Ratoon Stunting Disease of Sugarcane and Bermudagrass Stunting Disease†

Fluorescence is of diagnostic value for differentiating among species of aerobic pseudomonads (R. Y. Stanier, N. J. Palleroni, and M. Doudoroff, J. Gen. Microbiol. 43:159, 1966). The standard medium for detecting fluorescence is Medium B (E. 0. King, M. K. Ward, and D. E. Raney, J. Lab. Clin. Med. 44:301, 1954), which supports amino acids (J. De Ley, Ann. Rev. Microbiol. 18:17, 1964), and peptones (E. 0. King et al., J. Lab. Clin. Med. 44:301, 1954) affect fluorescence. The effect of carbon sources had not been shown. Although glycerol, glucose, or maltose can be used interchangeably in Medium B for detecting fluorescence of most fluorescent pseudo-

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Synthetic and complex media for the rapid detection of fluorescence of phytopathogenic pseudomonads: effect of the carbon source.

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1096&context=plantpathpapers

Anne K. Vidaver

Papers

Isolation and Characterization of Endophytic Colonizing Bacteria from Agronomic Crops and Prairie Plants

Bacteriophage φ6: a Lipid-Containing Virus of Pseudomonas phaseolicola

Clavibacter: a New Genus Containing Some Phytopathogenic Coryneform Bacteria, Including Clavibacter xyli subsp. xyli sp. nov., subsp. nov. and Clavibacter xyli subsp. cynodontis subsp. nov., Pathogens That Cause Ratoon Stunting Disease of Sugarcane and Bermudagrass Stunting Disease†

Synthetic and complex media for the rapid detection of fluorescence of phytopathogenic pseudomonads: effect of the carbon source.

Emended classification of xanthomonad pathogens on citrus