Different Levels Of Pathogenicity Research Articles

Wide Distribution and Intraspecies Diversity in the Pathogenicity of Calonectria in Soil from Eucalyptus Plantations in Southern Guangxi of China.

Eucalyptus spp. are extensively cultivated in southern China because of their adaptability and versatile timber production. Calonectria leaf blight caused by Calonectria species is considered a major threat to Eucalyptus trees planted in China. The GuangXi Zhuang Autonomous Region is the provincial region with the largest distribution of Eucalyptus plantations in China. The present study aimed to expound the species diversity and pathogenicity of Calonectria isolates obtained from the soil of Eucalyptus plantations in GuangXi. A total of 188 Calonectria isolates were recovered from the soil located close to Eucalyptus trees, and the isolates were identified based on the DNA sequence comparisons of the four partial regions of the translation elongation factor 1-alpha (tef1), β-tubulin (tub2), calmodulin (cmdA), and histone H3 (his3) genes. The isolates were identified as Calonectria aconidialis (74.5%), C. hongkongensis (21.3%), C. pseudoreteaudii (2.1%), C. kyotensis (1.6%), and C. chinensis (0.5%). The inoculation results indicated that 40 isolates representing five Calonectria species were pathogenic to the three Eucalyptus genotypes. Two inoculated experiments consistently showed that the longest lesions were produced by the isolates of C. aconidialis. Some isolates of C. aconidialis, C. hongkongensis, and C. kyotensis produced significantly longer lesions than the positive controls, but not the isolates of C. pseudoreteaudii or C. chinensis. These results indicated that Calonectria isolated from the soil may pose a threat to Eucalyptus plantations. Some Calonectria isolates of the same species differed significantly in their virulence in the tested Eucalyptus genotypes. The resistance of different Eucalyptus genotypes to Calonectria isolates within the same species was inconsistent. The inoculation results in this study suggested that many Calonectria isolates in each species had different levels of pathogenicity, and many Eucalyptus genotypes need to be tested to select disease-resistant Eucalyptus genetic materials in the future. The results of the present study enhance our knowledge of species diversity and the potential damage caused by Calonectria in the soil of Eucalyptus plantations. Our results also provide new insights into the breeding of disease-resistant Eucalyptus genotypes for controlling Calonectria leaf blight in China in the future.

Alterations in energy metabolism of Rhodnius prolixus induced by Trypanosoma rangeli infection

Trypanosoma rangeli is a protozoan parasite that infects triatomines and mammals in the Americas, producing mixed infections with Trypanosoma cruzi, the etiological agent of Chagas disease. The former parasite is not pathogenic to humans, but has different levels of pathogenicity, as well as causing physiological and behavioral alterations, to its invertebrate hosts. In this study, we measured locomotory activity, and the glyceride accumulation profile in the hemolymph and fat body, as well as the expression of key genes related to triglyceride metabolism, of Rhodnius prolixus nymphs infected with T. rangeli. We found that the locomotory activity of the insects was correlated with the amount of triglycerides in the fat body. Infected nymphs had increased activity when starved, and also had an accumulation of glycerides in the fat body and hemolymph. These alterations were also associated with a higher expression of the diacylglycerol acyltransferase, lipophorin and lipophorin receptor genes in the fat body. We infer that T. rangeli is able to alter the energetic processes of its invertebrate host, in order to increase the availability of lipids to the parasite, which, in turn modifies the activity levels of the insect. These alterations are discussed with regard to their potential to increase the transmission rate of the parasite.

Understanding the effects of carbon and nitrogen starvation on the comparative secretomes of Ganoderma boninense and Ganoderma tornatum

Ganoderma boninense is the most pathogenic fungal species of oil palm trees. However, there is limited understanding of the host - pathogen interaction. Secreted proteins play a critical role during the early infection process which involves competition between the fungal and host populations for nutrient resources necessary for continual growth. To identify the secreted proteins that may play a role in pathogenicity during infection stage, we compared the secretome profiles of G. boninense versus G. tornatum under carbon and nitrogen starvation by using shotgun proteomics approach. In total, 250 non-redundant proteins were identified, and statistical data analysis indicated that 68 proteins were increased while 104 proteins decreased in abundance in T3 for G. boninense whereas in G. tornatum, 42 proteins were increased, and 27 proteins were decreased in abundance in T3. Further investigation via bioinformatic tools helped us to classify the carbohydrate-active enzymes (CAZymes) proteins into four classes: oxidoreductases, transferases, hydrolases, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Interestingly, oxidoreductase enzymes were identified only in G. boninense. These putative proteins might contribute to the different levels of pathogenicity of G. boninense and G. tornatum toward oil palm. The newly discovered protein information may help researchers better understand the secretory mechanisms of G. boninense and the process by which it invades oil palm root tissues. The discovered seretome proteins, along with their subclassification and functional annotation also serve as a database for Ganoderma species that is easy to access and retrieve.

Pathogenicity and Transcriptomic Analyses of Two "Candidatus Liberibacter asiaticus" Strains Harboring Different Types of Phages.

"Candidatus Liberibacter asiaticus" is one of the putative causal agents of citrus Huanglongbing (HLB), a highly destructive disease threatening the global citrus industry. Several types of phages had been identified in "Ca. Liberibacter asiaticus" strains and found to affect the biology of "Ca. Liberibacter asiaticus." However, little is known about the influence of phages in "Ca. Liberibacter asiaticus" pathogenicity. In this study, two "Ca. Liberibacter asiaticus" strains, PYN and PGD, harboring different types of phages were collected and used for pathogenicity analysis in periwinkle (Catharanthus roseus). Strain PYN carries a type 1 phage (P-YN-1), and PGD harbors a type 2 phage (P-GD-2). Compared to strain PYN, strain PGD exhibited a faster reproduction rate and higher virulence in periwinkle: leaf symptoms appeared earlier, and there was a stronger inhibition in the growth of new flush. Estimation of phage copy numbers by type-specific PCR indicated that there are multiple copies of phage P-YN-1 in strain PYN, while strain PGD carries only a single copy of phage P-GD-2. Genome-wide gene expression profiling revealed the lytic activity of P-YN-1 phage, as evidenced by the unique expression of genes involved in lytic cycle, which may limit the propagation of strain PYN and lead to a delayed infection in periwinkle. However, the activation of genes involved in lysogenic conversion of phage P-GD-1 indicated it could reside within the "Ca. Liberibacter asiaticus" genome as a prophage form in strain PGD. Comparative transcriptome analysis showed that the significant differences in expression of virulence factor genes, including genes associated with pathogenic effectors, transcriptional factors, the Znu transport system, and the heme biosynthesis pathway, could be another major determinant of virulence variation between two "Ca. Liberibacter asiaticus" strains. This study expanded our knowledge of "Ca. Liberibacter asiaticus" pathogenicity and provided new insights into the differences in pathogenicity between "Ca. Liberibacter asiaticus" strains. IMPORTANCE Citrus Huanglongbing (HLB), also called citrus greening disease, is a highly destructive disease threatening citrus production worldwide. "Candidatus Liberibacter asiaticus" is one of the most common putative causal agents of HLB. Phages of "Ca. Liberibacter asiaticus" have recently been identified and found to affect "Ca. Liberibacter asiaticus" biology. Here, we found that "Ca. Liberibacter asiaticus" strains harboring different types of phages (type 1 or type 2) showed different levels of pathogenicity and multiplication patterns in the periwinkle plant (Catharanthus roseus). Transcriptome analysis revealed the possible lytic activity of type 1 phage in a "Ca. Liberibacter asiaticus" strain, which could limit the propagation of "Ca. Liberibacter asiaticus" and lead to the delayed infection in periwinkle. The heterogeneity in the transcriptome profiles, particularly the significant differences in expression of virulence factors genes, could be another major determinant of difference in virulence observed between the two "Ca. Liberibacter asiaticus" strains. These findings improved our understanding of "Ca. Liberibacter asiaticus"-phage interaction and provided insight into "Ca. Liberibacter asiaticus" pathogenicity.

Genome resource announcement for two isolates of Phytophthora sansomeana with varying levels of pathogenicity on soybean

Phytophthora sansomeana was recently recognized as a distinct species in 2009, it has since been detected in Phytophthora surveys across the North central region of the United States in recent years. Two isolates of P. sansomeana with moderate and high levels of pathogenicity (Psan_MP and Psan_HP, respectively), based on lesion development on soybean tap roots, were chosen for Oxford Nanopore Technologies (ONT) long-read genome sequencing to allow within-species genomic comparisons between isolates with different levels of pathogenicity on soybean. The genome assembly size, number of predicted protein-encoding genes, and number of candidate effectors was greater in the highly pathogenic isolate (Psan_HP) than the moderately pathogenic isolate (Psan_MP). Future work should more closely examine the context of P. sansomeana pathogenicity mechanisms relative to other Phytophthora species.

Trypanosoma rangeli infection impairs reproductive success of Rhodnius prolixus.

Trypanosoma rangeli is a protozoan that infects triatomines and mammals in Central and South America. Although it does not cause disease to humans, this parasite produces different levels of pathogenicity to its invertebrate host, mainly in species of the genus Rhodnius. In this study, we followed T. rangeli-infected and uninfected pairs throughout their adult lives and measured the amount of blood ingested, number of eggs laid, number of eggs hatched and proportion of infertile eggs, as well as female life expectancy. We found that all reproductive parameters were drastically decreased during infection, mainly due to the reduced amount of blood the infected insects ingested throughout their lives. Reproductive parameters were also affected by the reduction of the life expectancy of infected females, as survival was positively correlated with the number of eggs laid. The strategies used by the parasite to be transmitted are discussed in view of the pathological effects it causes in the insect.

Progress in 50 years of viroid research-Molecular structure, pathogenicity, and host adaptation.

Viroids are non-encapsidated, single-stranded, circular RNAs consisting of 246–434 nucleotides. Despite their non-protein-encoding RNA nature, viroids replicate autonomously in host cells. To date, more than 25 diseases in more than 15 crops, including vegetables, fruit trees, and flowers, have been reported. Some are pathogenic but others replicate without eliciting disease. Viroids were shown to have one of the fundamental attributes of life to adapt to environments according to Darwinian selection, and they are likely to be living fossils that have survived from the pre-cellular RNA world. In 50 years of research since their discovery, it was revealed that viroids invade host cells, replicate in nuclei or chloroplasts, and undergo nucleotide mutation in the process of adapting to new host environments. It was also demonstrated that structural motifs in viroid RNAs exert different levels of pathogenicity by interacting with various host factors. Despite their small size, the molecular mechanism of viroid pathogenicity turned out to be more complex than first thought.

Pathogenic and molecular variation of Fusarium species causing head blight on barley landraces

AbstractFusarium head blight (FHB) is consistently one of the most important barley diseases worldwide. This study aimed to evaluate the pathogenicity of 16 isolates of four Fusarium species under controlled conditions and their genetic variability using 22 random amplified polymorphic DNA (RAPD) markers. Pathogenic variation was characterized based on disease development rates and disease index on two Syrian barley landraces with varying resistance to FHB, Arabi Aswad (AS) and Arabi Abiad (AB). Significant differences in intra- and inter-Fusarium species pathogenicity and in susceptibility between the above-mentioned cultivars were highlighted. Overall, the two barley landraces showed moderately susceptible to moderately resistance levels to fungal infection and FHB spread within the head. Quantitative traits showed significant correlation with previous data generated in vitro and under field conditions, suggesting that growth chamber indices can predict fungal pathogenicity and quantitative disease resistance generated under various experimental conditions. Based on PCR amplification with seven different primers, the isolates showed genetic variation. Dendrogram generated by cluster analysis based on RAPD markers data showed two main groups, suggesting that a possible clonal origin could exist in the four Fusarium species. RAPD fingerprints are not useful to distinguish the 16 Fusarium isolates with different levels of pathogenicity.

Telomeres and a repeat-rich chromosome encode effector gene clusters in plant pathogenic Colletotrichum fungi.

Members of the Colletotrichum gloeosporioides species complex are causal agents of anthracnose in many commercially important plants. Closely related strains have different levels of pathogenicity on hosts despite their close phylogenetic relationship. To gain insight into the genetics underlying these differences, we generated and annotated whole-genome assemblies of multiple isolates of C. fructicola (Cf) and C. siamense (Cs), as well as three previously unsequenced species, C. aenigma (Ca), C. tropicale and C. viniferum with different pathogenicity on strawberry. Based on comparative genomics, we identified accessory regions with a high degree of conservation in strawberry-pathogenic Cf, Cs and Ca strains. These regions encode homologs of pathogenicity-related genes known as effectors, organized in syntenic gene clusters, with copy number variations in different strains of Cf, Cs and Ca. Analysis of highly contiguous assemblies of Cf, Cs and Ca revealed the association of related accessory effector gene clusters with telomeres and repeat-rich chromosomes and provided evidence of exchange between these two genomic compartments. In addition, expression analysis indicated that orthologues in syntenic gene clusters showed a tendency for correlated gene expression during infection. These data provide insight into mechanisms by which Colletotrichum genomes evolve, acquire and organize effectors.

Effect of seed-borne fungi on seed health of native populations of Iranian cumin (Cuminum cyminum L.)

Seed borne diseases caused by fungal pathogens are one of the most important threats that reduce the quantity and quality of cumin production every year all over the world. Hence, the first step in this research was to identify the seed-borne fungi obtained from seeds of native populations of Iranian cumin (Cuminum cyminum L.), their effect on germination and vigor indices, the location of fungi in seeds and their transmission into seedlings. Based on morphological and molecular characters, the fungi were identified as Alternaria alternata, A. burnsii, Fusarium oxysporum and F. solani. Most of the identified isolates were present in the seed coat, while a few isolates of A. alternata was located in embryos. The results revealed that a negative correlation were found between incidences of naturally fungi infected seed, germination, and vigor indices. The pathogenicity test revealed that 20% of the isolates were non-pathogenic and other isolates were pathogenic or weakly pathogenic. In addition, the percentage seed transmission of fungal phytopathogens to cumin seedlings revealed that A. alternata was the more frequently isolated (67.27%) followed by F. oxysporum (52.80%), A. burnsii (32.74%) and F. solani (20.01%). Then, we investigated correlation among the activities of cell wall degrading enzymes (CWDEs) produced by fungal isolates and variation in pathogenicity and aggressiveness in vivo. Different levels of pathogenicity and aggressiveness were observed for various isolates of Fusarium and Alternaria species. Analysis of CWDEs activities, including cellulase, xylanase, pectinase and lipase showed that cellulase and lipase activities were more important than xylanase and pectinase activities for the pathogenicity of isolates. Therefore, these findings suggested that activity levels of cellulase and lipase are correlated with variation in pathogenicity and aggressiveness of seed-borne fungal isolates on seedling. This is the first report on isolation and identification of seed-borne fungi infection of cumin, together with investigating association between pathogenesis and CWDEs production by isolates isolated from seeds of Iranian cumin native populations. It is also the first time that the location of fungi in seeds and its seed-transmitted into cumin seedlings have been identified and evaluated, respectively.

Cryptococcus neoformans: Sex, morphogenesis, and virulence.

Cryptococcus neoformans is a dimorphic fungus that causes lethal meningoencephalitis mainly in immunocompromised individuals. Different morphotypes enable this environmental fungus and opportunistic pathogen to adapt to different natural niches and exhibit different levels of pathogenicity in various hosts. It is well-recognized that C. neoformans undergoes bisexual or unisexual reproduction in vitro to generate genotypic, morphotypic, and phenotypic diversity, which augments its ability for adaptation. However, if and how sexual reproduction and the meiotic machinery exert any direct impact on the infection process is unclear. This review summarizes recent discoveries on the regulation of cryptococcal life cycle and morphogenesis, and how they impact cryptococcal pathogenicity. The potential role of the meiotic machinery on ploidy regulation during cryptococcal infection is also discussed. This review aims to stimulate further investigation on links between fungal morphogenesis, sexual reproduction, and virulence.

Pathogenicity Levels of Colombian Strains of Candida auris and Brazilian Strains of Candida haemulonii Species Complex in Both Murine and Galleria mellonella Experimental Models.

Candida auris and Candida haemulonii complex (C. haemulonii, C. haemulonii var. vulnera and C. duobushaemulonii) are phylogenetically related species that share some physiological features and habits. In the present study, we compared the virulence of these yeast species using two different experimental models: (i) Galleria mellonella larvae to evaluate the survival rate, fungal burden, histopathology and phagocytosis index and (ii) BALB/c mice to evaluate the survival. In addition, the fungal capacity to form biofilm over an inert surface was analyzed. Our results showed that in both experimental models, the animal survival rate was lower when infected with C. auris strains than the C. haemulonii species complex. The hemocytes of G. mellonella showed a significantly reduced ability to phagocytize the most virulent strains forming the C. haemulonii species complex. Interestingly, for C. auris, it was impossible to measure the phagocytosis index due to a general lysis of the hemocytes. Moreover, it was observed a greater capability of biofilm formation by C. auris compared to C. haemulonii species complex. In conclusion, we observed that C. auris and C. haemulonii complex have different levels of pathogenicity in the experimental models employed in the present study.

Genotyping Echinococcus multilocularis in Human Alveolar Echinococcosis Patients: An EmsB Microsatellite Analysis.

For clinical epidemiology specialists, connecting the genetic diversity of Echinococcus multilocularis to sources of infection or particular sites has become somewhat of a holy grail. It is very difficult to trace the infection history of alveolar echinococcosis (AE) patients as there may be an incubation period of five to 15 years before reliable diagnosis. Moreover, the variability of parasitic manifestations in human patients raises the possibility of genetically different isolates of E. multilocularis having different levels of pathogenicity. Thus, the exposure of human patients to different strains or genotypes circulating in geographically different environments may lead to different disease outcomes. Molecular tools, such as the microsatellite marker EmsB, were required to investigate these aspects. This genetic marker was previously tested on a collection of 1211 European field samples predominantly of animal origin, referenced on a publicly available database. In this study, we investigated a panel of 66 metacestode samples (between 1981 and 2019) recovered surgically from 63 patients diagnosed with alveolar echinococcosis originating from four European countries (France, Switzerland, Germany, Belgium). In this study, we identified nine EmsB profiles, five of which were found in patients located in the same areas of France and Switzerland. One profile was detected on both sides of the French-Swiss border, whereas most patients from non-endemic regions clustered together in another profile. EmsB profiles appeared to remain stable over time because similar profiles were detected in patients who underwent surgery recently and patients who underwent surgery some time ago. This study sheds light on possible pathways of contamination in humans, including proximity contamination in some cases, and the dominant contamination profiles in Europe, particularly for extrahepatic lesions.

Symptomatic and asymptomatic cases of African swine fever in Tanzania.

African swine fever (ASF) is an acute, highly contagious and deadly viral haemorrhagic disease of domestic pigs caused by African swine fever virus (ASFV). In ASF endemic countries, there are an increasing number of reports on circulating ASFV strains with different levels of virulence causing a broad range of clinical symptoms in susceptible animals. Tanzania, where ASFV is endemic since 2001, recorded several outbreaks including symptomatic and asymptomatic cases between 2015 and 2017. We collected 35 clinical samples from four outbreaks for diagnostic confirmation and sequenced the partial B646L (p72), the full E183L (p54) gene, the central variable region of the B602L gene and the intergenic region between the I73R and I329L genes to characterize molecularly the new ASFV isolates and analyse their relatedness with previously reported Tanzanian and foreign isolates. We detected ASFV in 21 samples, 15 from symptomatic and six from asymptomatic pigs. Phylogenetic analyses based on the partial p72 gene and the complete p54 (E183L) genes revealed that the ASFVs in samples from symptomatic pigs belonged to genotypes II and those in samples from asymptomatic pigs belonged to genotype IX. The CVR profiles of the p72 genotype II and genotype IX isolates differed between each other and from previously published Tanzanian sequences. The sequence analysis of the intergenic region between the I73R and I329L for the 2017 genotype II isolates showed the absence of one GGAATATATA motif in those isolates. This study showed the simultaneous circulation of two different ASFV genotypes with different levels of pathogenicity in Tanzania. Since the existence of sub-clinically infected pigs may contribute to the persistence of the virus, our findings suggest continuous surveillance and characterization of ASFV isolates in disease-endemic regions.

Incidence and Molecular Identification of Cochliobolus carbonum as Causal Organism of Rice Seedling Blight

During last few years, seedling blight and black lesions along culm of rice seedlings have been appearing frequently in nurseries. Identification of the causal organism was the objective of this research. The identification was done based on morpho-pathological characteristics and Internal Transcribed Spacer (ITS) region sequencing analysis. The pathogen effects on germination and development of rice seedlings were studied under laboratory and greenhouse conditions. Based on the morphological examination, 10 isolates were identified as Cochliobolus carbonum fungus. This organism recorded different levels of pathogenicity, and most of the isolates showed high virulence, up to 56% as seedling infection with isolate ECC-5. The germination percentage was reduced to 73% for cultivar Sakha 101. Sakha 101 recorded highest infected seedlings percentage (44%) under artificial inoculation. The isolates’ reaction was more variable on seedlings than on leaves of Egyptian rice cultivars. Infection severity on leaves of isolate ECC-5 recorded highest average for infection, while isolate ECC-3 did not exhibit any infection. Most of C. carbonum isolates were induced severe infection on rice seedlings. Therefore, the identified isolates were recorded as a novel pathogen causing seedling blight disease on rice. Soaking in crude extract filtrate of C. carbonium isolates culture reduced germination percentage to 1.55% with Sakha101 and inhibit the shoots and roots growth. The molecular variation using ISJ markers reflected a high level of genetic variation between isolates. The ITS region sequencing of two isolates ECC-7 and ECC-9 was successfully analyzed, and alignment with 19 isolates of Bipolaris zeicola worldwide with 97% identity. Phylogenetic analyses of sequences resulted in a well-resolved phylogeny. The data suggested that ITS region analysis was a potential tool for phylogenetic reconstruction of the new isolates and as was DNA barcode for identification of the fungal species. It confirmed that this organism is a rice seed-borne pathogen that causes seedling blight disease.

Evidence for an effect of landscape connectivity on Borrelia burgdorferi sensu stricto dispersion in a zone of range expansion

In North America, different strains of the Lyme disease-causing bacterium Borrelia burgdorferi sensu stricto cluster into phylogenetic groups that are associated with different levels of pathogenicity and, for some, specific rodent reservoir hosts. Here we explore whether landscape connectivity, by impacting host dispersal, influences B. burgdorferi s.s. spread patterns. This question is central to modelling spatial patterns of the spread of Lyme disease risk in the zone of northward range-expansion of B. burgdorferi s.s. in southeastern Canada where the study was conducted. We used multi-locus sequence typing (MLST) to characterise B. burgdorferi s.s. in positive ticks collected at 13 sites in southern Quebec, Canada during the early stages of B. burgdorferi s.s. invasion. We used mixed effects logistic regression to investigate whether landscape connectivity (probability of connectivity; PC) affected the probability that samples collected at different sites were of the same strain (MLST sequence type: ST). PC was calculated from a habitat map based on high spatial resolution (15 m) Landsat 8 imagery to identify woodland habitat that are preferred by rodent hosts of B. burgdorferi s.s. There was a significant positive association between the likelihood that two samples were of the same ST and PC, when PC values were grouped into three categories of low, medium and high. When analysing data for individual STs, samples at different sites were significantly more likely to be the same when PC was higher for the rodent-associated ST1. These findings support the hypothesis that dispersion trajectories of B. burgdorferi s.s. in general, and some rodent-associated strains in particular, are at least partly determined by landscape connectivity. This may suggest that dispersion of B. burgdorferi s.s. is more common by terrestrial mammal hosts (which would likely disperse according to landscape connectivity) than by birds, the dispersal of which is likely less constrained by landscape. This study suggests that accounting for landscape connectivity may improve model-based predictions of spatial spread patterns of B. burgdorferi s.s. The findings are consistent with possible past dispersal patterns of B. burgdorferi s.s. as determined by phylogeographic studies.

Detection and characterisation of potentially pathogenic species of Vibrio in the Vibrata river, Abruzzo Region, Italy.

This study aimed to isolate, define the genetic profile, assess potential pathogenicity and evaluate the seasonal distribution of Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus strains isolated from the Vibrata river (Abruzzo Region, Italy) during a monitoring period of one year. Detection was performed according to ISO/TS 21872-1-2:2007. Species identification and characterisation were achieved using molecular methods. Vibrio spp. were detected in 50% (23) of the water samples. In particular, V. cholerae, V. parahaemolyticus, and V. vulnificus were isolated in 18 (39.1%), 4 (8.7%), and 2 (4.3%) samples, respectively. All V. parahaemolyticus strains were tdh gene negative, 75% were positive for trh gene. In 30 V. cholerae isolates, the polymerase chain reaction (PCR) assay for detecting virulence and regulatory genes (ctxA, toxR, tcpA, ompU, hlyA, tcpI, zot, and stn/sto) revealed 6 genotypes associated to different levels of pathogenicity. Pulsed-field gel electrophoresis (PFGE) characterisation of the V. cholerae strains identified 13 different pulsotypes. A greater degree of similarity was shown for strains isolated in the same period of the year. Results of our study reveal a potential health risk associated with the waters of the Vibrata river, which are used for irrigation and next to the swimming areas of Abruzzo coastline.

Hydrogen peroxide production and myo-inositol metabolism as important traits for virulence of Mycoplasma hyopneumoniae.

Mycoplasma hyopneumoniae is the causative agent of enzootic pneumonia. In our previous work, we reconstructed the metabolic models of this species along with two other mycoplasmas from the respiratory tract of swine: Mycoplasma hyorhinis, considered less pathogenic but which nonetheless causes disease and Mycoplasma flocculare, a commensal bacterium. We identified metabolic differences that partially explained their different levels of pathogenicity. One important trait was the production of hydrogen peroxide from the glycerol metabolism only in the pathogenic species. Another important feature was a pathway for the metabolism of myo-inositol in M. hyopneumoniae. Here, we tested these traits to understand their relation to the different levels of pathogenicity, comparing not only the species but also pathogenic and attenuated strains of M. hyopneumoniae. Regarding the myo-inositol metabolism, we show that only M. hyopneumoniae assimilated this carbohydrate and remained viable when myo-inositol was the primary energy source. Strikingly, only the two pathogenic strains of M. hyopneumoniae produced hydrogen peroxide in complex medium. We also show that this production was dependent on the presence of glycerol. Although further functional tests are needed, we present in this work two interesting metabolic traits of M. hyopneumoniae that might be directly related to its enhanced virulence.

Effect of temperature and vector nutrition on the development and multiplication of Trypanosoma rangeli in Rhodnius prolixus.

Trypanosoma rangeli is a protozoan parasite that infects mammals and triatomines, causing different levels of pathogenicity in its invertebrate vectors, particularly those from the genus Rhodnius. We have recently shown that temperature can modulate T. rangeli growth during in vitro culture, as well as its in vivo pathogenicity to R. prolixus. In the present study, we investigated colonization of R. prolixus by T. rangeli and assessed the role of temperature and vector nutrition on parasite development and multiplication. We infected nymphs and either assessed parasite density in the first hours after the ingestion of the infected blood or maintained the nymphs for up to 60days at different temperatures (21, 24, 27, and 30°C) and under different blood-feeding schedules (either every 15days, or on day 30 post infection only), with parasite development and multiplication measured on days 15, 30, and 60 post infection. In the first hours after ingesting infected blood, epimastigogenesis not only occurred in the anterior midgut, but a stable parasite population also established in this intestinal region. T. rangeli subsequently colonized all intestinal regions examined, but with fewer parasites being found in the rectum. The number of parasites was only affected by higher temperatures (27 and 30°C) during the beginning of the infection (15days post infection). Nutritional status of the vector also had a significant effect on parasite development, as reduced blood-feeding decreased infection rates by approximately 30%.

Identification and function of FAR protein family genes from a transcriptome analysis of Aphelenchoides besseyi.

The rice white tip nematode (RWTN) Aphelenchoides besseyi is a migratory plant parasitic nematode that infects the aboveground parts of plants. Fatty acid- and retinoid-binding (FAR) proteins are nematode-specific proteins that are involved in many important biological processes. Genes encoding FAR proteins have been identified in many species of nematodes, which indicated that nematodes may produce more than one type of FAR protein. The main goal of this study is to find new molecular targets including new far genes that will help control RWTN, and reduce the economic damage caused by RWTN. Two RWTN populations with different levels of pathogenicity and reproduction were sequenced and analyzed with next-generation sequencing. 17 087 transcripts were annotated using six databases and 1696 differentially expressed genes (DEGs) were identified between the two RWTN populations. Seven new Ab-far genes were identified from the transcriptome data of the two RWTN populations which is the first to identify multiple far genes in plant parasitic nematodes. This study is the first to identify far genes in the nervous system of nematodes and the first to report a transcriptome sequencing analysis of different RWTN populations. The results help elucidate the genes related to parasitism and pathogenicity and also contribute to the identification of new target genes and development of new methods to control RWTN. Our data are publicly available at Sequence Read Archive (SRA) database and GenBank database. Supplementary data are available at Bioinformatics online.