Chlamydia trachomatis is a globally important obligate intracellular bacterial pathogen that is a leading cause of sexually transmitted disease and blinding trachoma. Effective control of these diseases will likely require a preventative vaccine. C. trachomatis polymorphic membrane protein D (PmpD) is an attractive vaccine candidate as it is conserved among C. trachomatis strains and is a target of broadly cross-reactive neutralizing antibodies. We show here that immunoaffinity-purified native PmpD exists as an oligomer with a distinct 23-nm flower-like structure. Two-dimensional blue native-sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses showed that the oligomers were composed of full-length PmpD (p155) and two proteolytically processed fragments, the p73 passenger domain (PD) and the p82 translocator domain. We also show that PmpD undergoes an infection-dependent proteolytic processing step late in the growth cycle that yields a soluble extended PD (p111) that was processed into a p73 PD and a novel p30 fragment. Interestingly, soluble PmpD peptides possess putative eukaryote-interacting functional motifs, implying potential secondary functions within or distal to infected cells. Collectively, our findings show that PmpD exists as two distinct forms, a surface-associated oligomer exhibiting a higher-order flower-like structure and a soluble form restricted to infected cells. We hypothesize that PmpD is a multifunctional virulence factor important in chlamydial pathogenesis and could represent novel vaccine or drug targets for the control of human chlamydial infections.Chlamydia trachomatis is a mucosotropic obligate intracellular gram-negative pathogen that is a leading cause of sexually transmitted and ocular infections. Infection can result in serious sequelae such as infertility and blindness (54, 56) and an increased risk of human immunodeficiency virus infection and transmission (38). The pathophysiology of chlamydial infection is associated with the pathogen's propensities to cause persistent infection and to suppress host immunity (3). A vaccine is needed to control chlamydial diseases; however, progress toward this goal will not be forthcoming until more is known about the virulence factors that mediate persistence and immune evasion.Chlamydiae are characterized by a unique biphasic developmental cycle that modulates between an extracellular, metabolically inactive, infectious elementary body (EB) and an intracellular, metabolically active, noninfectious reticulate body (RB) (34). Their obligate intracellular niche and the lack of a tractable genetic system present unique challenges in the study of chlamydial biology and pathogenesis. To overcome these hurdles, chlamydial genomes from a diverse spectrum of hostspecific strains have been sequenced. Comparative genomics have shown considerable homology among various chlamydial species and have provided important insights into shared and species-specific virulence factors (7,24,41,42,46,49).The type V or autotransporter (AT) secretion p...

The unicellular eukaryotic algae Cyanidium, Galdieria, and Cyanidioschyzon (herein referred to as ''cyanidia'') are the only photoautotrophs occurring in acidic (pH<4.0) geothermal environments at temperatures above 401C. In Yellowstone National Park (YNP), we examined an annual event we refer to as ''mat decline,'' where cyanidial mats undergo a seasonably defined color fading. Monthly sampling of chemical, physical, and biological features revealed that spring aqueous chemistry was essentially invariant over the 1-year sampling period. However, multiple regression analysis suggested that a significant proportion of algal most probable number (MPN) count variation could be explained by water temperature and UV-visible (VIS) light exposure. Irradiance manipulations (filtering) were then coupled with 14 CO 2 incorporation experiments to directly demonstrate UV inhibition of photosynthesis. Population dynamics were also evident in 18S rDNA PCR clone libraries, which were different in composition at MPN maxima and minima, and again evident in PCR-amplified chloroplast genomic short sequence repeat (SSR) analysis. PCR-cloned SSRs of the YNP isolates and mats were very similar to Cyanidioschyzon merolae Luca, Taddei et Varano, although distance analysis could distinguish the YNP cyanidia from the genome sequenced C. merolae that was isolated in Italy. Unexpectedly, while phylogenetic analysis of 18S rDNA sequences and SSR sequences derived from YNP cyanidial mats and pure cultures suggested these algae are most closely related to C. merolae (99.7% identity), cell morphology was consistent with the genera Galdieria and Cyanidium.