BackgroundThe Amoebozoa constitute one of the primary divisions of eukaryotes, encompassing taxa of both biomedical and evolutionary importance, yet its genomic diversity remains largely unsampled. Here we present an analysis of a whole genome assembly of Acanthamoeba castellanii (Ac) the first representative from a solitary free-living amoebozoan.ResultsAc encodes 15,455 compact intron-rich genes, a significant number of which are predicted to have arisen through inter-kingdom lateral gene transfer (LGT). A majority of the LGT candidates have undergone a substantial degree of intronization and Ac appears to have incorporated them into established transcriptional programs. Ac manifests a complex signaling and cell communication repertoire, including a complete tyrosine kinase signaling toolkit and a comparable diversity of predicted extracellular receptors to that found in the facultatively multicellular dictyostelids. An important environmental host of a diverse range of bacteria and viruses, Ac utilizes a diverse repertoire of predicted pattern recognition receptors, many with predicted orthologous functions in the innate immune systems of higher organisms.ConclusionsOur analysis highlights the important role of LGT in the biology of Ac and in the diversification of microbial eukaryotes. The early evolution of a key signaling facility implicated in the evolution of metazoan multicellularity strongly argues for its emergence early in the Unikont lineage. Overall, the availability of an Ac genome should aid in deciphering the biology of the Amoebozoa and facilitate functional genomic studies in this important model organism and environmental host.

This multinational study from Asia revealed that reduced susceptibility to ciprofloxacin (MIC, 0.125 to 1 g/ml) in nontyphoid Salmonella isolates was common in Taiwan (48.1%) and Thailand (46.2%) and in S. enterica serotype Choleraesuis (68.8%) and S. Virchow (75.0%) from all countries. Reduced susceptibility to ceftriaxone (MIC, 2 to 8 g/ml) remained uncommon in Asia, except in Taiwan (38.0%) or in S. Typhimurium (25.0%) from all countries.Nontyphoid Salmonella bacteria, with more than 2,500 serotypes, usually cause diarrheal diseases in humans that may be complicated by extraintestinal infections, such as bacteremia, meningitis, and osteomyelitis (11). Resistance to antimicrobial agents, including fluoroquinolones and expanded-spectrum cephalosporins, has been a serious problem worldwide. Nontyphoid salmonellosis has been rampant in Asia (7); however, data on the antimicrobial susceptibilities, as well as the prevalence, of various serotypes in many Asian countries after 2000 have been lacking.During 2003 to 2005, 400 clinical isolates of nontyphoid Salmonella bacteria were randomly collected from 11 medical centers in seven Asian countries (Table 1) and transported to the central laboratory in Samsung Medical Center, Seoul, Korea, for serogrouping and serotyping using O and H antisera, respectively (Difco Laboratories, Detroit, MI). Susceptibilities to ciprofloxacin, tetracycline, ceftriaxone, ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole were determined by a broth microdilution method, and the results were interpreted according to the breakpoints for MICs suggested by the NCCLS (10). For statistical analysis, isolates in the "intermediate" category were deemed "resistant" in this study. Concomitant resistance to at least three of the six antibiotics tested was defined as multidrug resistance (MDR). Isolates with ciprofloxacin MICs of 0.125 to 1 g/ml were defined as having "reduced susceptibility" to ciprofloxacin (9). Similarly, "reduced susceptibility" to ceftriaxone was defined as isolates showing ceftriaxone MICs of 2 to 8 g/ml (14). These definitions were proposed in previous reports to reflect the clinical therapeutic responses (9, 14). The 2 test and Student's t test were used to determine the significance of differences, and a P value of Ͻ0.05 was considered statistically significant.A total of nine serogroups (B, C1, C2, D, E, G, I, K, and M) and 82 serotypes were identified among the isolates tested. Serogroups B (34.8%) and D (25.0%) were the two leading serogroups in all areas except Philippines, where serogroup E (25 isolates, 53.2%) was most prevalent. The distribution of major serotypes among the countries is shown in Table 1. Overall, S. enterica serotype Enteritidis and S. Typhimurium were the two most-prevalent serotypes except in Philippines, Singapore, and Thailand, where S. Weltevreden was either the most-or second-most-prevalent serotype. In Sri Lanka and Thailand, the most-prevalent serotypes were S. Agona and S. Stanley, respectively. S. Choleraesuis was relatively mor...

BackgroundIron plays a pivotal role in the pathogenesis of Trichomonas vaginalis, the causative agent of highly prevalent human trichomoniasis. T. vaginalis resides in the vaginal region, where the iron concentration is constantly changing. Hence, T. vaginalis must adapt to variations in iron availability to establish and maintain an infection. The free radical signaling molecules reactive oxygen species (ROS) and reactive nitrogen species (RNS) have been proven to participate in iron deficiency in eukaryotes. However, little is known about the roles of these molecules in iron-deficient T. vaginalis.MethodsT. vaginalis cultured in iron-rich and -deficient conditions were collected for all experiments in this study. Next generation RNA sequencing was conducted to investigate the impact of iron on transcriptome of T. vaginalis. The cell viabilities were monitored after the trophozoites treated with the inhibitors of nitric oxide (NO) synthase (L-NG-monomethyl arginine, L-NMMA) and proteasome (MG132). Hydrogenosomal membrane potential was measured using JC-1 staining.ResultsWe demonstrated that NO rather than ROS accumulates in iron-deficient T. vaginalis. The level of NO was blocked by MG132 and L-NMMA, indicating that NO production is through a proteasome and arginine dependent pathway. We found that the inhibition of proteasome activity shortened the survival of iron-deficient cells compared with untreated iron-deficient cells. Surprisingly, the addition of arginine restored both NO level and the survival of proteasome-inhibited cells, suggesting that proteasome-derived NO is crucial for cell survival under iron-limited conditions. Additionally, NO maintains the hydrogenosomal membrane potential, a determinant for cell survival, emphasizing the cytoprotective effect of NO on iron-deficient T. vaginalis. Collectively, we determined that NO produced by the proteasome prolonged the survival of iron-deficient T. vaginalis via maintenance of the hydrogenosomal functions.ConclusionThe findings in this study provide a novel role of NO in adaptation to iron-deficient stress in T. vaginalis and shed light on a potential therapeutic strategy for trichomoniasis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-015-1000-5) contains supplementary material, which is available to authorized users.