scholarly journals Phylogenomic Analysis of Secondary Metabolism in the Toxic Cyanobacterial Genera Anabaena, Dolichospermum and Aphanizomenon

Toxins ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 248 ◽  
Author(s):  
Julia Österholm ◽  
Rafael V. Popin ◽  
David P. Fewer ◽  
Kaarina Sivonen
Keyword(s):  
Health Risks ◽  
Taxonomic Revision ◽  
Toxin Production ◽  
Toxin Gene ◽  
Phylogenomic Analysis ◽  
Phylogenetic Clustering ◽  
Brackish Waters ◽  
Constituent Species ◽  
The World ◽  
Taxonomic Confusion

Cyanobacteria produce an array of toxins that pose serious health risks to humans and animals. The closely related diazotrophic genera, Anabaena, Dolichospermum and Aphanizomenon, frequently form poisonous blooms in lakes and brackish waters around the world. These genera form a complex now termed the Anabaena, Dolichospermum and Aphanizomenon (ADA) clade and produce a greater array of toxins than any other cyanobacteria group. However, taxonomic confusion masks the distribution of toxin biosynthetic pathways in cyanobacteria. Here we obtained 11 new draft genomes to improve the understanding of toxin production in these genera. Comparison of secondary metabolite pathways in all available 31 genomes for these three genera suggests that the ability to produce microcystin, anatoxin-a, and saxitoxin is associated with specific subgroups. Each toxin gene cluster was concentrated or even limited to a certain subgroup within the ADA clade. Our results indicate that members of the ADA clade encode a variety of secondary metabolites following the phylogenetic clustering of constituent species. The newly sequenced members of the ADA clade show that phylogenetic separation of planktonic Dolichospermum and benthic Anabaena is not complete. This underscores the importance of taxonomic revision of Anabaena, Dolichospermum and Aphanizomenon genera to reflect current phylogenomic understanding.

A taxonomic revision of Cheilodactylidae and Latridae (Centrarchiformes: Cirrhitoidei) using morphological and genomic characters

Zootaxa ◽  
2019 ◽  
Vol 4585 (1) ◽  
pp. 121
Author(s):  
WILLIAM B. LUDT ◽  
CHRISTOPHER P. BURRIDGE ◽  
PROSANTA CHAKRABARTY
Keyword(s):  
South African ◽  
Type Species ◽  
New Genus ◽  
Taxonomic Revision ◽  
African Species ◽  
The Past ◽  
The Family ◽  
The World ◽  
Taxonomic Confusion ◽  
Systematic Relationships

Systematic relationships within the Cirrhitoidei, a suborder of five closely related families, have been uncertain for over a century. This is particularly true in reference to the families Cheilodactylidae and Latridae, which have been revised numerous times over the past several decades. Species that have been included in these two families are found in temperate regions around the world, which has led to regionally-focused studies that have only exacerbated taxonomic confusion. Here we examine systematic relationships within the Cheilodactylidae and the Latridae using ultraconserved genomic elements with near complete taxonomic sampling, and place our results in the context of the Cirrhitoidei. Our results agree with previous findings suggesting that Cheilodactylidae is restricted to two South African species, with the type species of the family, Cheilodactylus fasciatus Lacépède, forming a clade with C. pixi Smith that together is more closely related to the Chironemidae than to other species historically associated with the genus. We also strongly resolve the relationships of species within the Latridae. As a result of our analyses we revise the taxonomy of Latridae, name a new genus, and re-elevate Chirodactylus and Morwong. 

System of generic groups in mealybugs (Homoptera: Coccinea: Pseudococcidae)

2015 ◽  
Vol 24 (2) ◽  
pp. 236-259 ◽  
Author(s):  
I.A. Gavrilov-Zimin
Keyword(s):  
Taxonomic Revision ◽  
Generic Rank ◽  
The World ◽  
Generic Groups ◽  
World Fauna

The paper provides a brief conspectus of the system of morphological generic groups, elaborated earlier by the author basing on the total taxonomic revision of Palaearctic mealybugs. Here the system is complemented by the analysis of all 249 genera of the world fauna. Borders of two generic groups are reconsidered and two else groups (with mainly Oriental and Australasian genera) are included in the system. Main taxonomic characters of generic rank are discussed and illustrated.

scholarly journals Temporal Variations in Patterns of Clostridioides difficile Strain Diversity and Antibiotic Resistance in Thailand

Antibiotics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 714
Author(s):  
Supapit Wongkuna ◽  
Tavan Janvilisri ◽  
Matthew Phanchana ◽  
Phurt Harnvoravongchai ◽  
Amornrat Aroonnual ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Antimicrobial Susceptibility ◽  
Reference Strain ◽  
Toxin Production ◽  
Temporal Variations ◽  
Toxin Gene ◽  
Data Sets ◽  
Clostridioides Difficile ◽  
Life Threatening ◽  
Susceptibility Profiles

Clostridioides difficile has been recognized as a life-threatening pathogen that causes enteric diseases, including antibiotic-associated diarrhea and pseudomembranous colitis. The severity of C. difficile infection (CDI) correlates with toxin production and antibiotic resistance of C. difficile. In Thailand, the data addressing ribotypes, toxigenic, and antimicrobial susceptibility profiles of this pathogen are scarce and some of these data sets are limited. In this study, two groups of C. difficile isolates in Thailand, including 50 isolates collected from 2006 to 2009 (THA group) and 26 isolates collected from 2010 to 2012 (THB group), were compared for toxin genes and ribotyping profiles. The production of toxins A and B were determined on the basis of toxin gene profiles. In addition, minimum inhibitory concentration of eight antibiotics were examined for all 76 C. difficile isolates. The isolates of the THA group were categorized into 27 A−B+CDT− (54%) and 23 A-B-CDT- (46%), while the THB isolates were classified into five toxigenic profiles, including six A+B+CDT+ (23%), two A+B+CDT− (8%), five A−B+CDT+ (19%), seven A−B+CDT− (27%), and six A−B−CDT− (23%). By visually comparing them to the references, only five ribotypes were identified among THA isolates, while 15 ribotypes were identified within THB isolates. Ribotype 017 was the most common in both groups. Interestingly, 18 unknown ribotyping patterns were identified. Among eight tcdA-positive isolates, three isolates showed significantly greater levels of toxin A than the reference strain. The levels of toxin B in 3 of 47 tcdB-positive isolates were significantly higher than that of the reference strain. Based on the antimicrobial susceptibility test, metronidazole showed potent efficiency against most isolates in both groups. However, high MIC values of cefoxitin (MICs 256 μg/mL) and chloramphenicol (MICs ≥ 64 μg/mL) were observed with most of the isolates. The other five antibiotics exhibited diverse MIC values among two groups of isolates. This work provides evidence of temporal changes in both C. difficile strains and patterns of antimicrobial resistance in Thailand.

Haemolytic activity in different species of the genus Prymnesium (Haptophyta)

2016 ◽  
Vol 97 (3) ◽  
pp. 491-496 ◽  
Author(s):  
S. Seoane ◽  
P. Riobó ◽  
J. Franco
Keyword(s):  
Stationary Phases ◽  
Growth Conditions ◽  
Economic Losses ◽  
Haemolytic Activity ◽  
Brackish Waters ◽  
Extraction Solvent ◽  
Fatty Acid Amides ◽  
The World ◽  
Allelopathic Effects ◽  
Different Strains

The genus Prymnesium includes several species that produce toxins with cytotoxic, ichthyotoxic, neurotoxic and haemolytic activity. Bloom episodes of Prymnesium species have been reported from several parts of the world (North America, Europe, Africa, Asia and Australia), especially from temperate and subtropical regions and most of them from brackish waters. Blooms cause great economic losses to aquaculture and fisheries around the world. The ichthyotoxic and allelopathic effects of Prymnesium have been linked to the presence of Haemolysin 1, Prymnesins 1 and 2 and, more recently, fatty acids and fatty acid amides. The toxicology of this genus with regard to different growth conditions such as light, nutrients and other parameters has been well documented. It is unknown, however, whether different species and strains from the Prymnesium genus all produce the same types and level of toxins. In this study, we have determined the haemolytic activity of eight different strains from the genus Prymnesium in both exponential and stationary phases of growth. We have also evaluated the efficiency of the extraction solvent.

scholarly journals FliW and CsrA Govern Flagellin (FliC) Synthesis and Play Pleiotropic Roles in Virulence and Physiology of Clostridioides difficile R20291

2021 ◽  
Vol 12 ◽  
Author(s):  
Duolong Zhu ◽  
Shaohui Wang ◽  
Xingmin Sun
Keyword(s):  
Bacterial Colonization ◽  
Toxin Production ◽  
Toxin Gene ◽  
Clostridioides Difficile ◽  
Significant Difference ◽  
Assembly Factor ◽  
Carbon Storage Regulator ◽  
Transcription Suppression ◽  
Post Transcriptional Regulation

Clostridioides difficile flagellin FliC is associated with toxin gene expression, bacterial colonization, and virulence, and is also involved in pleiotropic gene regulation during in vivo infection. However, how fliC expression is regulated in C. difficile remains unclear. In Bacillus subtilis, flagellin homeostasis and motility are coregulated by flagellar assembly factor (FliW), flagellin Hag (FliC homolog), and Carbon storage regulator A (CsrA), which is referred to as partner-switching mechanism “FliW-CsrA-Hag.” In this study, we characterized FliW and CsrA functions by deleting or overexpressing fliW, csrA, and fliW-csrA in C. difficile R20291. We showed that fliW deletion, csrA overexpression in R20291, and csrA complementation in R20291ΔWA (fliW-csrA codeletion mutant) dramatically decreased FliC production, but not fliC gene transcription. Suppression of fliC translation by csrA overexpression can be relieved mostly when fliW was coexpressed, and no significant difference in FliC production was detected when only fliW was complemented in R20291ΔWA. Further, loss of fliW led to increased biofilm formation, cell adhesion, toxin production, and pathogenicity in a mouse model of C. difficile infection (CDI), while fliW-csrA codeletion decreased toxin production and mortality in vivo. Our data suggest that CsrA negatively modulates fliC expression and FliW indirectly affects fliC expression through inhibition of CsrA post-transcriptional regulation. In light of “FliW-CsrA-Hag” switch coregulation mechanism reported in B. subtilis, our data also suggest that “FliW-CsrA-fliC/FliC” can regulate many facets of C. difficile R20291 pathogenicity. These findings further aid us in understanding the virulence regulation in C. difficile.

scholarly journals Distribution of the Intermedilysin Gene among the Anginosus Group Streptococci and Correlation between Intermedilysin Production and Deep-Seated Infection with Streptococcus intermedius

2000 ◽  
Vol 38 (1) ◽  
pp. 220-226
Author(s):  
Hideaki Nagamune ◽  
Robert A. Whiley ◽  
Takatsugu Goto ◽  
Yasuko Inai ◽  
Takuya Maeda ◽  
...  
Keyword(s):  
Southern Hybridization ◽  
Marker Gene ◽  
Toxin Production ◽  
Clear Correlation ◽  
Toxin Gene ◽  
Hemolysis Assay ◽  
Streptococcus Intermedius ◽  
Triggering Factor ◽  
Peripheral Infection ◽  
Human Specific

ABSTRACT The distribution of intermedilysin, a human-specific cytolysin, among the anginosus group streptococci and the correlation of toxin production and infection by Streptococcus intermedius were investigated. PCR and Southern hybridization specific for the intermedilysin gene revealed that the toxin gene exists only in S. intermedius and no homologue to the toxin gene is distributed in S. anginosus and S. constellatus . Thus, the intermedilysin gene is useful as a marker gene of S. intermedius . Moreover, a human-specific hemolysis assay and Western blotting with intermedilysin-specific antibodies clearly demonstrated that the intermedilysin production level in isolates from deep-seated infections, such as brain and liver abscesses, is higher (6.2- to 10.2-fold, respectively) than in strains from normal habitats, such as dental plaque, or from peripheral infection sites. However, other candidate virulence factors of S. intermedius , such as chondroitin sulfate depolymerase, hyaluronidase, and sialidase activities, did not show such a clear correlation between enzymatic activity and isolation sites or disease severity. From these results, intermedilysin is likely to be the pathogenic or triggering factor of significance in inducing deep-seated infections with S. intermedius .

scholarly journals New edition of International Travel and Health book from WHO

2002 ◽  
Vol 6 (9) ◽  
Author(s):  
M Ciotti
Keyword(s):  
Infectious Diseases ◽  
Incubation Period ◽  
Health Risks ◽  
International Travel ◽  
Upward Trend ◽  
The World

International travel is undertaken by large, and ever increasing, numbers of people. More people travel longer distances and at greater speed than ever before; an upward trend that looks set to continue. Travellers are thus exposed to a variety of health risks in unfamiliar environments. Most of these risks, however, can be minimised by suitable precautions taken before, during, and after travel. Virtually any place in the world can be reached within 36 hours, less than the incubation period for most infectious diseases.

scholarly journals A critique of the World Resources Institute's report "Pesticides and the immune system: the public health risks".

1998 ◽  
Vol 106 (2) ◽  
pp. 51-54 ◽  
Author(s):  
J Acquavella ◽  
C Burns ◽  
D Flaherty ◽  
M Holsapple ◽  
I Kimber ◽  
...  
Keyword(s):  
Public Health ◽  
Immune System ◽  
Health Risks ◽  
The Public ◽  
Public Health Risks ◽  
The World

scholarly journals RstA Is a Major Regulator ofClostridioides difficileToxin Production and Motility

mBio ◽  
2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Adrianne N. Edwards ◽  
Brandon R. Anjuwon-Foster ◽  
Shonna M. McBride
Keyword(s):  
Gene Expression ◽  
Dna Binding ◽  
Toxin Production ◽  
Toxin Gene ◽  
Dna Binding Domain ◽  
Content Type ◽  
Toxin Genes ◽  
Clostridioides Difficile ◽  
Species Specific ◽  
Toxin Gene Expression

ABSTRACTClostridioides difficileinfection (CDI) is a toxin-mediated diarrheal disease. Several factors have been identified that influence the production of the two majorC. difficiletoxins, TcdA and TcdB, but prior published evidence suggested that additional unknown factors were involved in toxin regulation. Previously, we identified aC. difficileregulator, RstA, that promotes sporulation and represses motility and toxin production. We observed that the predicted DNA-binding domain of RstA was required for RstA-dependent repression of toxin genes, motility genes, andrstAtranscription. In this study, we further investigated the regulation of toxin and motility gene expression by RstA. DNA pulldown assays confirmed that RstA directly binds therstApromoter via the predicted DNA-binding domain. Through mutational analysis of therstApromoter, we identified several nucleotides that are important for RstA-dependent transcriptional regulation. Further, we observed that RstA directly binds and regulates the promoters of the toxin genestcdAandtcdB, as well as the promoters for thesigDandtcdRgenes, which encode regulators of toxin gene expression. Complementation analyses with theClostridium perfringensRstA ortholog and a multispecies chimeric RstA protein revealed that theC. difficileC-terminal domain is required for RstA DNA-binding activity, suggesting that species-specific signaling controls RstA function. Our data demonstrate that RstA is a transcriptional repressor that autoregulates its own expression and directly inhibits transcription of the two toxin genes and two positive toxin regulators, thereby acting at multiple regulatory points to control toxin production.IMPORTANCEClostridioides difficileis an anaerobic, gastrointestinal pathogen of humans and other mammals.C. difficileproduces two major toxins, TcdA and TcdB, which cause the symptoms of the disease, and forms dormant endospores to survive the aerobic environment outside the host. A recently discovered regulatory factor, RstA, inhibits toxin production and positively influences spore formation. Herein, we determine that RstA directly binds its own promoter DNA to repress its own gene transcription. In addition, our data demonstrate that RstA directly represses toxin gene expression and gene expression of two toxin gene activators, TcdR and SigD, creating a complex regulatory network to tightly control toxin production. This study provides a novel regulatory link betweenC. difficilesporulation and toxin production. Further, our data suggest thatC. difficiletoxin production is regulated through a direct, species-specific sensing mechanism.

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