Mitochondrial Large Ribosomal Subunit Research Articles

The zinc finger motif in the mitochondrial large ribosomal subunit protein bL36m is essential for optimal yeast mitoribosome assembly and function

Ribosomes across species contain subsets of zinc finger proteins that play structural roles by binding to rRNA. While the majority of these zinc fingers belong to the C2-C2 type, the large subunit protein L36 in bacteria and mitochondria exhibits an atypical C2-CH motif. To comprehend the contribution of each coordinating residue in S. cerevisiae bL36m to mitoribosome assembly and function, we engineered and characterized strains carrying single and double mutations in the zinc coordinating residues. Our findings reveal that although all four residues markedly influence protein stability, C to A mutations in C66 and/or C69 have a more pronounced effect compared to those at C82 and H88. Importantly, protein stability directly correlates with the assembly and function of the mitoribosome and the growth rate of yeast in respiratory conditions. Mass spectrometry analysis of large subunit particles indicates that strains deleted for bL36m or expressing mutant variants have defective assembly of the L7/L12 stalk base, limiting their functional competence. Furthermore, we employed a synthetic bL36m protein collection, including both wild-type and mutant proteins, to elucidate their ability to bind zinc. Our data indicate that mutations in C82 and, particularly, H88 allow for some zinc binding albeit inefficient or unstable, explaining the residual accumulation and activity in mitochondria of bL36m variants carrying mutations in these residues. In conclusion, stable zinc binding by bL36m is essential for optimal mitoribosome assembly and function. MS data are available via ProteomeXchange with identifierPXD046465.

Weighted gene co-expression network analysis of key targets and interventional mechanism of Milkvetch root in diabetic nephropathy.

This work aimed to explore the key targets and intervention mechanisms of Huangqi (Astragalus membranaceus) in diabetic nephropathy using weighted gene co-expression network analysis (WGCNA). The findings will provide references for identifying critical therapeutic targets for diabetic nephropathy. The GSE1009 dataset was selected from the Gene Expression Omnibus (GEO) database of the National Center for Biotechnology Information (NCBI) for analysis. WGCNA network was constructed to identify differentially expressed genes (DEGs). Gene ontology (GO) and pathway enrichment analysis were performed on the DEGs. There were 752 downregulated DEGs and 1,547 upregulated DEGs in the diabetic nephropathy samples. Genes such as PLCE1, CLIC5, PTPRO, HSPA12A, AIF1, GMDS, and SEMA5A were significantly suppressed in the diabetic nephropathy samples, while genes such as CEP152, LUNAR1, and SLC9A1 were significantly upregulated. The optimal soft threshold for the WGCNA network was determined as 12. Hierarchical clustering analysis was conducted to detect co-expression modules with corresponding color assignments, and a total of 9 modules were identified. Clinical characteristics showed a high correlation with the gray, blue, green, and brown modules of the WGCNA. GO analysis and KEGG pathway enrichment analysis revealed that the blue module DEGs were mainly enriched in immune response, inflammatory response, signal transduction, plasma membrane, extracellular region, cell surface, extracellular matrix, and proteinaceous extracellular matrix. The green module DEGs were mainly enriched in mitochondrial elongation, mitochondrial mutation termination, translation, mitochondrial inner membrane, mitochondrion, ATP biosynthetic process, mitochondrial large ribosomal subunit, mitochondrial intermembrane space, nucleolus, and ribosome. Visualization analysis of the bioactive components of Huangqi showed compounds such as quercetin, resveratrol, 7-O-methylisomucronulatol, and isoquercetin, which had more targets. Differentially expressed genes in diabetic nephropathy were mainly enriched in immune response and inflammatory response. Various components of Huangqi have positive application value in the treatment of diabetic nephropathy and can be considered for clinical promotion.

Low Expression of Mitofusin 1 Gene Leads to Mitochondrial Dysfunction and Embryonic Genome Activation Failure in Ovine-Bovine Inter-Species Cloned Embryos.

Inter-species somatic cell nuclear transfer (iSCNT) is significant in the study of biological problems such as embryonic genome activation and the mitochondrial function of embryos. Here, we used iSCNT as a model to determine whether abnormal embryo genome activation was caused by mitochondrial dysfunction. First, we found the ovine-bovine iSCNT embryos were developmentally blocked at the 8-cell stage. The reactive oxygen species level, mitochondrial membrane potential, and ATP level in ovine-bovine cloned embryos were significantly different from both bovine-bovine and IVF 8-cell stage embryos. RNA sequencing and q-PCR analysis revealed that mitochondrial transport, mitochondrial translational initiation, mitochondrial large ribosomal subunit, and mitochondrial outer membrane genes were abnormally expressed in the ovine-bovine embryos, and the mitochondrial outer membrane and mitochondrial ribosome large subunit genes, mitochondrial fusion gene 1, and ATPase Na+/K+ transporting subunit beta 3 gene were expressed at lower levels in the ovine-bovine cloned embryos. Furthermore, we found that overexpression and knockdown of Mfn1 significantly affected mitochondrial fusion and subsequent biological functions such as production of ATP, mitochondrial membrane potential, reactive oxygen species and gene expressions in cloned embryos. These findings enhance our understanding of the mechanism by which the Mfn1 gene regulates embryonic development and embryonic genome activation events.

Corynoneura Winnertz species from Hunan Province, Oriental China, delineated with morphological and 16S rDNA data (Diptera, Chironomidae).

The genus Corynoneura Winnertz, 1846 from Hunan Province in Oriental China is reviewed. Four new species, C.enormis Fu sp. nov., C.gibbera Fu sp. nov., C.incuria Fu sp. nov., and C.longshanensis Fu sp. nov. are described and illustrated based on adult males. Sequence data from the 16S rDNA gene were used to infer relationships between these species and complement morphological delineation. Sequences from the mitochondrial large ribosomal subunit (16S rDNA) from these species are uploaded to the National Center for Biotechnology Information (NCBI). Relationships were inferred using the Neighbor-Joining method based on 16S rDNA.

The mitochondrial genome sequence analysis of Ophidascaris baylisi from the Burmese python (Python molurus bivittatus).

Ophidascaris species are parasitic roundworms that inhabit the python gut, resulting in severe granulomatous lesions or even death. However, the classification and nomenclature of these roundworms are still controversial. Our study aims to identify a snake roundworm from the Burmese python (Python molurus bivittatus) and analyze the mitochondrial genome. We identified this roundworm as Ophidascaris baylisi based on the morphology and cytochrome c oxidase subunit I (cox1) sequence. Ophidascaris baylisi complete mitochondrial genome was 14,784bp in length, consisting of two non-coding regions and 36 mitochondrial genes (12 protein-coding genes, 22 tRNA genes, and two rRNA genes). The protein-coding genes used TTG, ATG, ATT, or TTA as start codons and TAG, TAA, or T as stop codons. All tRNA genes showed a TV-loop structure, except trnS1AGN and trnS2UCN revealed a D-loop structure. The mitochondrial large ribosomal subunit 16S (rrnL) and small ribosomal subunit 12S (rrnS) were 956bp and 700bp long, respectively. Phylogenetic analysis based on O. baylisi mitochondrial protein-coding genes demonstrated that O. baylisi clustered with the family Ascarididae members and was most closely related to Ophidascaris wangi. These results may enhance the nematode mitochondrial genome database and provide valuable molecular markers for further research on the taxonomy, phylogeny, and genetic relationships of Ophidascaris nematodes.

Structural basis of GTPase-mediated mitochondrial ribosome biogenesis and recycling

Ribosome biogenesis requires auxiliary factors to promote folding and assembly of ribosomal proteins and RNA. Particularly, maturation of the peptidyl transferase center (PTC) is mediated by conserved GTPases, but the molecular basis is poorly understood. Here, we define the mechanism of GTPase-driven maturation of the human mitochondrial large ribosomal subunit (mtLSU) using endogenous complex purification, in vitro reconstitution and cryo-EM. Structures of transient native mtLSU assembly intermediates that accumulate in GTPBP6-deficient cells reveal how the biogenesis factors GTPBP5, MTERF4 and NSUN4 facilitate PTC folding. Addition of recombinant GTPBP6 reconstitutes late mtLSU biogenesis in vitro and shows that GTPBP6 triggers a molecular switch and progression to a near-mature PTC state. Additionally, cryo-EM analysis of GTPBP6-treated mature mitochondrial ribosomes reveals the structural basis for the dual-role of GTPBP6 in ribosome biogenesis and recycling. Together, these results provide a framework for understanding step-wise PTC folding as a critical conserved quality control checkpoint.

Traditional Knowledge Aids Description When Resolving the Taxonomic Status of Unsettled Species Using Classical and Molecular Taxonomy: The Case of the Shallow-Water Octopus Callistoctopus furvus (Gould, 1852) From the Western Atlantic Ocean

Shallow-water marine invertebrate fauna is diverse in tropical latitudes but generally poorly known. This is in part due the remoteness of many of these regions, and a lack of locally trained taxonomists. In such cases, the ethnoknowledge (i.e., information acquired from the sociocultural references of a given social group) of traditional human populations may be a valuable tool to elucidate gaps in the occurrence of some taxa. In this study, we used a combined approach of ethnoknowledge, classic taxonomy and molecular techniques to describe and diagnose an unsettled species of shallow-water octopus of the genusCallistoctopus. A neotype for the Brazilian eastern octopusCallistoctopus furvus(Gould, 1852) is described along with some ecological notes. Octopuses were collected between April and May 2018 during field trips guided by artisanal octopus fishers of Bahia State (Brazil). A linear discriminant analysis showed that the morphology ofC. furvusoverlapped poorly withCallistoctopussp. from the Caribbean and Macaronesia (Madeira Archipelago) as well as withCallistoctopus macropus stricto sensufrom Mediterranean Sea. Analysis of mitochondrial large ribosomal subunit (rrnL, also known as 16S) gene and cytochrome C oxidase I (COI) showed thatC. furvusdiffers genetically from EuropeanC. macropusand the other species in the genus. In general,C. furvusdiffers from other Atlantic/MediterraneanCallistoctopusspecies in having a slender body shape and longer mantle lengths. As in other species of the genus,C. furvusis nocturnal and inhabits sandy bottoms, seagrass beds and/or low-profile reefs. Interestingly,C. furvusburrows itself into the sand as a defense mechanism. In conclusion, we showed the support of ethnoknowledge for integrative biodiversity assessments in poorly surveyed remote areas in the western tropical Atlantic.

RCC1L (WBSCR16) isoforms coordinate mitochondrial ribosome assembly through their interaction with GTPases.

Mitochondrial translation defects can be due to mutations affecting mitochondrial- or nuclear-encoded components. The number of known nuclear genes involved in mitochondrial translation has significantly increased in the past years. RCC1L (WBSCR16), a putative GDP/GTP exchange factor, has recently been described to interact with the mitochondrial large ribosomal subunit. In humans, three different RCC1L isoforms have been identified that originate from alternative splicing but share the same N-terminus, RCC1LV1, RCC1LV2 and RCC1LV3. All three isoforms were exclusively localized to mitochondria, interacted with its inner membrane and could associate with homopolymeric oligos to different extent. Mitochondrial immunoprecipitation experiments showed that RCC1LV1 and RCC1LV3 associated with the mitochondrial large and small ribosomal subunit, respectively, while no significant association was observed for RCC1LV2. Overexpression and silencing of RCC1LV1 or RCC1LV3 led to mitoribosome biogenesis defects that resulted in decreased translation. Indeed, significant changes in steady-state levels and distribution on isokinetic sucrose gradients were detected not only for mitoribosome proteins but also for GTPases, (GTPBP10, ERAL1 and C4orf14), and pseudouridylation proteins, (TRUB2, RPUSD3 and RPUSD4). All in all, our data suggest that RCC1L is essential for mitochondrial function and that the coordination of at least two isoforms is essential for proper ribosomal assembly.

The grass squid Pickfordiateuthis pulchella is a paedomorphic loliginid

The wide disparity in adult body size observed both within and among animal taxa has long attracted widespread interest, with several general rules having been proposed to explain trends in body size evolution. Adult body size disparity among the cephalopod mollusks is remarkable, with adult body sizes ranging from a few centimeters to several meters. Some of the smallest cephalopods are found within Pickfordiateuthis, a group comprising three described species of squid found in the western Atlantic and tropical eastern Pacific. Pickfordiateuthis pulchella, the type species of the genus, was initially proposed to be closely related to the loliginid squids (Loliginidae), with subsequent descriptions of additional species supporting a placement within Loliginidae. Pickfordiateuthis is remarkable in that all species reach sexual maturity at about one-fifth to one-tenth the size seen in most loliginid species. To date, no phylogenetic analyses have included representatives of Pickfordiateuthis. To infer the phylogenetic position of Pickfordiateuthis and explore its implications for body size evolution, we collected specimens of Pickfordiateuthis pulchella from Brazilian waters and sequenced regions of two loci—the mitochondrial large ribosomal subunit (rrnL a.k.a. 16S) gene and the nuclear gene rhodopsin. Maximum likelihood and Bayesian analyses of these sequences support a placement of Pickfordiateuthis pulchella as sister to a clade comprising the Western Hemisphere loliginid genera Doryteuthis and Lolliguncula. Analyses of body size evolution within Loliginidae suggest that a shift to a smaller body size optimum occurred along the lineage leading to P. pulchella, with some evidence of shifts toward larger sizes in the ancestors of Loligo and Sepioteuthis; these inferences seem to be robust to phylogenetic uncertainty and incomplete taxon sampling. The small size and juvenile-like morphological traits seen in adult Pickfordiateuthis (e.g., sepiolid-like fins and biserial sucker arrangement in the tentacles) may be due to paedomorphosis.

Identification of key genes involved in the development and progression of early-onset colorectal cancer by co-expression network analysis.

A number of studies have revealed that there is an increasing incidence of early-onset colorectal cancer (CRC) in young adults (before the age of 50 years) and a progressive decline in CRC among older patients, after the age of 50 years (late-onset CRC). However, the etiology of early-onset CRC is not fully understood. The aim of the present study was to identify key genes associated with the development of early-onset CRC through weighted gene co-expression network analysis (WGCNA). The GSE39582 dataset was downloaded from the Gene Expression Omnibus database, and the data profiles of tissues from patients diagnosed before the age of 50 years were selected. The top 10,000 genes with the highest variability were used to construct the WGCNA. Hub genes were identified from the modules associated with clinical traits using gene significance >0.2 and module membership >0.8 as the cut-off criteria. Gene Ontology and pathway analyses were subsequently performed on the hub genes and a protein-protein interaction network (PPI) was constructed. The diagnostic value of module hub genes with a degree score >5 in the PPI network was verified in samples from patients with CRC diagnosed before the age of 50 years obtained from The Cancer Genome Atlas. Eight co-expressed gene modules were identified in the WGCNA and two modules (blue and turquoise) were associated with the tumor-node-metastasis stage. A total of 140 module hub genes were identified and found to be enriched in ‘mitochondrial large ribosomal subunit’, ‘structural constituent of ribosome’, ‘poly (A) RNA binding’, ‘collagen binding’, ‘protein ubiquitination’ and ‘ribosome pathway’. Twenty-six module hub genes were found to have a degree score >5 in the PPI network, seven of which [secreted protein acidic and cysteine rich (SPARC), decorin (DCN), fibrillin 1 (FBN1), WW domain containing transcription regulator 1 (WWTR1), transgelin (TAGLN), DEAD-box helicase 28 (DDX28) and cold shock domain containing C2 (CSDC2)], had good prognostic values for patients with early-onset CRC, but not late-onset CRC. Therefore, SPARC, DCN, FBN1, WWTR1, TAGLN, DDX28 and CSDC2 may contribute to the development of early-onset CRC and may serve as potential diagnostic biomarkers.

Polymorphisms involving the Pneumocystis jirovecii-related genes in AIDS patients in eastern China

ObjectiveTo investigate the genetic polymorphisms of mitochondrial large ribosomal subunit (mtLSU)-rRNA, dihydrofolate reductase (DHFR), dihydropteroate synthase (DHPS), cytochrome b (CYB), and superoxide dismutase (SOD) genes and its correlation with clinical outcomes of Pneumocystis jirovecii pneumonia in acquired immune deficiency(AIDS) patients. MethodsEighty AIDS patients with P. jirovecii pneumonia that were admitted to our hospital from 2016 to 2018 were included in this study. Their demographic information and clinical data were collected, as well as corresponding saliva specimens for PCR and sequencing of mtLSU-rRNA, DHFR, DHPS, CYB, and SOD genes to analyze genetic polymorphisms, different polymorphic combinations, and clinical outcomes. ResultsOf the 80 saliva specimens, mtLSU-rRNA was successfully amplified and sequenced in 30 cases; CYB was successfully amplified and sequenced in 26 cases; and SOD, DHFR, and DHPS were successfully amplified and sequenced in 18 cases. These results indicate that The mtLSU-rRNA, CYB, and SOD genes were highly polymorphic. mt85T and CYB1 were the variants dominantly detected at the mtLSU-rRNA and CYB loci, respectively. The SOD1 and SOD2 variants (each in 50% of the cases) were detected at the SOD locus. Among the 18 cases that were successfully amplified and sequenced for DHFR and DHPS, three DHFR nonsense mutations and no DHPS mutation were observed. The mt85C, CYB1, SOD1, and DHFR312T genes harbored common polymorphisms (n = 4; 22.22%) and the mt85T, CYB1, SOD1, DHFR312T genes were associated with poor clinical outcomes. ConclusionThe types of genetic polymorphisms and polymorphic combinations of mtLSU-rRNA, DHFR, DHPS, CYB, and SOD in P. jirovecii were related to the clinical outcomes of patients with P. jirovecii pneumonia in Zhejiang Province, China.

Molecular identification and characterization of Trichinella spiralis from a leopard in India

TPresent study describes species level identification of Trichinella spiralis of leopard origin from India using multiplex PCR and molecular characterization of the parasite based on sequencing of multiple genetic markers viz. 5S ribosomal DNA intergenic spacer region (5S ISR), partial mitochondrial large ribosomal subunit (Mt-lsr) and partial mitochondrial cytochrome c oxidase I (COI) genes. A single amplicons of 173 bp, indicative of T. spiralis was obtained in multiplex PCR. Further, specific PCR amplifications viz. 750 bp (5S ISR), 445 bp (Mt-lsr) and 850 bp (COI) were obtained for selected genetic markers. Homology search analysis of 5S-ISR, Mt-lsr gene and COI gene showed highest 99.6% identity with sequences originating from China (KT894074, T. spiralis), 98.6% similarity with T. spiralis China isolates (GU339127, GU339147) and 99.8% sequence homology with T. spiralis sequences originating from Belarus (MH119334), respectively. In the phylogenetic analysis, sequences of each selected genetic marker clustered together with published T. spiralis isolates only, which further confirmed species level identification of detected larvae as T. spiralis, although very few differences were noted with reference to relative positions. This is the first study from India, which provide molecular evidence on circulation of T. spiralis in wild animals.

PTCD1 Is Required for 16S rRNA Maturation Complex Stability and Mitochondrial Ribosome Assembly

The regulation of mitochondrial RNA life cycles and their roles in ribosome biogenesis and energy metabolism are not fully understood. We used CRISPR/Cas9 to generate heart- and skeletal-muscle-specific knockout mice of the pentatricopeptide repeat domain protein 1, PTCD1, and show that its loss leads to severe cardiomyopathy and premature death. Our detailed transcriptome-wide and functional analyses of these mice enabled us to identify the molecular role of PTCD1 as a 16S rRNA-binding protein essential for its stability, pseudouridylation, and correct biogenesis of the mitochondrial large ribosomal subunit. We show that impaired mitoribosome biogenesis can have retrograde signaling effects on nuclear gene expression through the transcriptional activation of the mTOR pathway and upregulation of cytoplasmic protein synthesis and pro-survival factors in the absence of mitochondrial translation. Taken together, our data show that impaired assembly of the mitoribosome exerts itsconsequences via differential regulation of mitochondrial and cytoplasmic protein synthesis.

Insight into higher-level phylogeny of Neuropterida: Evidence from secondary structures of mitochondrial rRNA genes and mitogenomic data.

It is well known that the rRNA structure information is important to assist phylogenetic analysis through identifying homologous positions to improve alignment accuracy. In addition, the secondary structure of some conserved motifs is highly stable among distantly related taxa, which can provide potentially informative characters for estimating phylogeny. In this paper, we applied the high-throughput pooled sequencing approach to the determination of neuropteran mitogenomes. Four complete mitogenome sequences were obtained: Micromus angulatus (Hemerobiidae), Chrysoperla nipponensis (Chrysopidae), Rapisma sp. (Ithonidae), and Thaumatosmylus sp. (Osmylidae). This allowed us to sample more complete mitochondrial RNA gene sequences. Secondary structure diagrams for the complete mitochondrial small and large ribosomal subunit RNA genes of eleven neuropterid species were predicted. Comparative analysis of the secondary structures indicated a closer relationship of Megaloptera and Neuroptera. This result was congruent with the resulting phylogeny inferred from sequence alignments of all 37 mitochondrial genes, namely the hypothesis of (Raphidioptera + (Megaloptera + Neuroptera)).

Metazoan mitochondrial gene sequence reference datasets for taxonomic assignment of environmental samples

Mitochondrial-encoded genes are increasingly targeted in studies using high-throughput sequencing approaches for characterizing metazoan communities from environmental samples (e.g., plankton, meiofauna, filtered water). Yet, unlike nuclear ribosomal RNA markers, there is to date no high-quality reference dataset available for taxonomic assignments. Here, we retrieved all metazoan mitochondrial gene sequences from GenBank, and then quality filtered and formatted the datasets for taxonomic assignments using taxonomic assignment tools. The reference datasets—‘Midori references’—are available for download at www.reference-midori.info. Two versions are provided: (I) Midori-UNIQUE that contains all unique haplotypes associated with each species and (II) Midori-LONGEST that contains a single sequence, the longest, for each species. Overall, the mitochondrial Cytochrome oxidase subunit I gene was the most sequence-rich gene. However, sequences of the mitochondrial large ribosomal subunit RNA and Cytochrome b apoenzyme genes were observed for a large number of species in some phyla. The Midori reference is compatible with some taxonomic assignment software. Therefore, automated high-throughput sequence taxonomic assignments can be particularly effective using these datasets.

Analysis of Spatiotemporal Genetic Variability in Eastern OysterCrassostrea virginica(Gmelin, 1791) Mtdna 16S Sequences Among North Carolina Populations

ABSTRACT Spatial and temporal genetic structure of the eastern oyster Crassostrea virginica was examined along the coast of North Carolina (NC); utilizing a fragment of the mitochondrial large (16S) ribosomal subunit gene sequence known to distinguish three regional haplotypes in C. virginica—North Atlantic, South Atlantic, and Gulf of Mexico. Significant geographic genetic structure was identified among all populations studied, with little temporal genetic variation observed over the 9-y sampling period. The results are consistent with those of previous studies analyzing geographic variation in mitochondrial DNA16S sequence data, which revealed a genetic discontinuity between North and South Atlantic oyster assemblages along the NC Coast. The increased geographic resolution and duration of sampling in this study revealed a sustained significant shift in genetic composition between Pamlico Sound populations and southern NC populations of C. virginica. These results suggest that a prolonged or persistent b...

Haploinsufficiency of the 22q11.2 microdeletion gene Mrpl40 disrupts short-term synaptic plasticity and working memory through dysregulation of mitochondrial calcium

Hemizygous deletion of a 1.5- to 3-megabase region on chromosome 22 causes 22q11.2 deletion syndrome (22q11DS), which constitutes one of the strongest genetic risks for schizophrenia. Mouse models of 22q11DS have abnormal short-term synaptic plasticity that contributes to working-memory deficiencies similar to those in schizophrenia. We screened mutant mice carrying hemizygous deletions of 22q11DS genes and identified haploinsufficiency of Mrpl40 (mitochondrial large ribosomal subunit protein 40) as a contributor to abnormal short-term potentiation (STP), a major form of short-term synaptic plasticity. Two-photon imaging of the genetically encoded fluorescent calcium indicator GCaMP6, expressed in presynaptic cytosol or mitochondria, showed that Mrpl40 haploinsufficiency deregulates STP via impaired calcium extrusion from the mitochondrial matrix through the mitochondrial permeability transition pore. This led to abnormally high cytosolic calcium transients in presynaptic terminals and deficient working memory but did not affect long-term spatial memory. Thus, we propose that mitochondrial calcium deregulation is a novel pathogenic mechanism of cognitive deficiencies in schizophrenia.

Spermatozoan ultrastructure and mitochondrial gene sequence of Caryocorbula caribaea (d'Orbigny, 1853) (Corbulidae: Bivalvia), a species with plasticity in shell morphology

Systematics of Corbulidae supported by anatomical and conchological studies remains confused and controversial because of the considerable phenotypic plasticity of their shells. Ultrastructural spermatozoan study and molecular analyses have been performed to contribute valuable information, which could be used in taxonomy. Electron microscopy was used to analyse sperm cells from specimens of Caryocorbula (Gardner, 1926) exhibiting shell differences. The spermatozoon was of the aquasperm type, showing short acrosome, barrel-shaped nucleus, midpiece composed of four spherical mitochondria and simple flagellum. In addition, about 860 base pairs of mitochondrial large ribosomal subunit (16S rRNA) were sequenced from each individual. The consistent similarity shared by spermatozoa and DNA sequences from all studied specimens indicated that they belonged to one coherent unit, Caryocorbula caribaea (d'Orbigny, 1853), despite the extraordinary plasticity exhibited by their shells.

Arbuscular mycorrhizal fungal communities and Rhizophagus irregularis populations shift in response to short-term ploughing and fertilisation in a buffer strip.

Short-term effects of soil physical disturbance by ploughing and nitrogen and phosphate fertilisation on arbuscular mycorrhizal fungal (AMF) communities and on intraspecific populations of Rhizophagus irregularis in a buffer strip surrounded by arable fields were studied. Pre-grown Plantago lanceolata plantlets were transplanted into fertilised and/or ploughed experimental plots. After 3months, the glomeromycotan communities in the roots of these trap plants were analysed using 454 pyrosequencing of a fragment of the RNA polymerase II gene (RPB1). Intraspecific populations of R. irregularis were studied by restriction fragment length polymorphism (RFLP) analysis of the mitochondrial large ribosomal subunit (mtLSU) gene. Soil disturbance significantly increased the diversity of species-level molecular taxa (MTs) and altered community structure, whilst fertilisation alone had no significant effect, unless coupled with ploughing. At the population level, the expected shift from genotypes of R. irregularis typically found in grasslands to those usually found in arable sites was only partially observed. In conclusion, in the short-term, physical soil disturbance, as well as nitrogen fertilisation when coupled with physical soil disturbance, affected AMF community and to a smaller extent population composition.

A genetic analysis of Trichuris trichiura and Trichuris suis from Ecuador.

BackgroundSince the nematodes Trichuris trichiura and T. suis are morphologically indistinguishable, genetic analysis is required to assess epidemiological cross-over between people and pigs. This study aimed to clarify the transmission biology of trichuriasis in Ecuador.FindingsAdult Trichuris worms were collected during a parasitological survey of 132 people and 46 pigs in Esmeraldas Province, Ecuador. Morphometric analysis of 49 pig worms and 64 human worms revealed significant variation. In discriminant analysis morphometric characteristics correctly classified male worms according to host species. In PCR-RFLP analysis of the ribosomal Internal Transcribed Spacer (ITS-2) and 18S DNA (59 pig worms and 82 human worms), nearly all Trichuris exhibited expected restriction patterns. However, two pig-derived worms showed a “heterozygous-type” ITS-2 pattern, with one also having a “heterozygous-type” 18S pattern. Phylogenetic analysis of the mitochondrial large ribosomal subunit partitioned worms by host species. Notably, some Ecuadorian T. suis clustered with porcine Trichuris from USA and Denmark and some with Chinese T. suis.ConclusionThis is the first study in Latin America to genetically analyse Trichuris parasites. Although T. trichiura does not appear to be zoonotic in Ecuador, there is evidence of genetic exchange between T. trichiura and T. suis warranting more detailed genetic sampling.