New insights into pollen morphology and its implications in the phylogeny of Sanguisorba L. (Rosaceae; Sanguisorbeae)

Pollen morphology of 13 species of the genus Sanguisorba (Rosaceae) was examined by light and scanning electron microscopy. The pollen morphology divided the genus into two main groups: (A) tricolporate with tapered colpus tips, and (B) either tricolporate with opened colpus tip or hexacolporate. The former group was further subdivided into those without vestibulum (A1: S.?alpina, S.?dodecandra, and S.?filiformis) and those with vestibulum (A2: S.?agrimonoides, S.?ancestroides, S.?annua, S.?cretica, S.?minor, and S.?verrucosa), whereas the latter group was subdivided into those with colpus narrow and similar to the A1 type (B1: S.?canadensis and S.?diandra), those with colpus and mesocolpus somewhat equally wide and forming hexacolporate aperture (B3: S.?albiflora, S.?armena, S.?media, S.?menziesii, S.?parviflora, S.?stipulata, and S.?tenuifolia), and those with colpus intermediate between the B1 and B3 types (B2: S.?hakusanensis, S.?microcephala, S.?obtusa, S.?officinalis, S.?polygama, and S.?sitchensis). It is suggested that the A1 type aperture would have evolved to the A2 type as a specialized form and the B types (B1 to B3) in a direction in which the hexacolporate aperture was derived. Implications of pollen morphology for infrageneric classification of Sanguisorba are discussed and the results are compared with molecular phylogenetic studies.     

The lipopolysaccharide core of Actinobacillus suis and its relationship to those of Actinobacillus pleuropneumoniae

The Gram-negative bacteria Actinobacillus suis colonizes the upper respiratory and genital tracts of swine. Along with capsular polysaccharides, lipopolysaccharides (O-chain→core→lipid A~cell) are a main cell-surface component of A.?suis. In this study, we determined that A.?suis lipopolysaccharide incorporates a conserved core that shares some structural features with several core types of A.?pleuropneumoniae . These common core structural features likely account for the observed serological cross-reactivity between A.?suis and A.?pleuropneumoniae, and the data suggest that the structural epitopes responsible for immunogenicity are those in the outer core domain.     

Morphological variability in rupicolous species of the Acianthera prolifera complex (Orchidaceae) occurring in southeastern Brazil

We carried out multivariate morphometric analysis of 23 floral characters in seven populations of a complex of four species of Acianthera (Orchidaceae) occurring in Brazilian campo rupestre (rocky field) vegetation (A.?hamosa, A.?limae, A.?modestissima, and A.?prolifera) that flower synchronously and are partially intercompatible, and one putative hybrid population between A.?limae and A.?prolifera. We also carried out cluster analysis involving these eight populations plus 21 populations of a previously published study belonging to another species complex of Acianthera occurring in campo rupestre, including 12 floral characters in the analysis. Allopatric species pollinated by the same group of Diptera showed higher floral similarity among themselves than to a sympatric species pollinated by another group of Diptera. Such patterns indicate the existence of floral convergence in allopatric species and/or radiation in sympatric species. The analysis also indicated that there is more floral similarity between species of different complexes but that share the same group of pollinators. Large overlap was observed between A.?limae and the putative sympatric hybrids, indicating the occurrence of later generations of hybrids and/or individuals of A.?limae with introgression. The results do not support A.?hamosa and A.?modestissima as distinct species. These taxa are geographically isolated, occurring in different environments, are recognized only by vegetative characters that show high phenotypic plasticity, and share the same pollinators, being interfertile.     

Imported fire ants near the edge of their range: disturbance and moisture determine prevalence and impact of an invasive social insect

1.?Habitat disturbance and species invasions interact in natural systems, making it difficult to isolate the primary cause of ecosystem degradation. A general understanding requires case studies of how disturbance and invasion interact across a variety of ecosystem - invasive species combinations. 2.?Dramatic losses in ant diversity followed the invasion of central Texas by red imported fire ants (Solenopsis invicta). However, recent manipulative studies in Florida revealed no effect on ant diversity following the removal of S.?invicta from a disturbed pasture habitat, but moderate loss of diversity associated with their introduction into undisturbed habitat and no invasion occurred without disturbance. Thus, the importance of S.?invicta in driving diversity loss and its ability to invade undisturbed systems is unresolved. 3.?We examine the distribution and abundance of a large monogyne S.?invicta population and its association with the co-occurring ant assemblage at a site in south Texas close to the aridity tolerance limit of S.?invicta. 4.?We document that moisture modulates S.?invicta densities. Further, soil disturbing habitat manipulations greatly increase S.?invicta population densities. However, S.?invicta penetrates all habitats regardless of soil disturbance history. In contrast, controlled burns depress S.?invicta densities. 5.?In habitats where S.?invicta is prevalent, it completely replaces native fire ants. However, S.?invicta impacts native ants as a whole less strongly. Intriguingly, native ants responded distinctly to S.?invicta in different environments. In wet, undisturbed environments, high S.?invicta abundance disrupts the spatial structure of the ant assemblage by increasing clumping and is associated with reduced species density, while in dry-disturbed habitats, sites with high S.?invicta abundance possess high numbers of native species. Analyses of co-occurrence indicate that reduced species density in wet-undisturbed sites arises from negative species interactions between native ants and S.?invicta. However, these same data suggest that the high native species density of abundant S.?invicta sites in dry-disturbed environments does not result from facilitation. 6.?Monogyne S.?invicta populations play different roles in different environments, driving ant diversity loss in some, but being largely symptomatic of habitat disturbance in others.     

A comparison of the clavam biosynthetic gene clusters in Streptomyces antibioticus Tü1718 and Streptomyces clavuligerus

The production of clavam metabolites has been studied previously in Streptomyces clavuligerus , a species that produces clavulanic acid as well as 4 other clavam compounds, but the late steps of the pathway leading to the specific end products are unclear. The present study compared the clavam biosynthetic gene cluster in Streptomyces antibioticus , chosen because it produces only 2 clavam metabolites and no clavulanic acid, with that of S.?clavuligerus. A cosmid library of S.?antibioticus genomic DNA was screened with a clavaminate synthase-specific probe based on the corresponding genes from S. clavuligerus, and 1 of the hybridizing cosmids was sequenced in full. A clavam gene cluster was identified that shows similarities to that of S.?clavuligerus but also contains a number of novel genes. Knock-out mutation of the clavaminate synthase gene abolished clavam production in S.?antibioticus, confirming the identity of the gene cluster. Knock-out mutation of a novel gene encoding an apparent oxidoreductase also abolished clavam production. A potential clavam biosynthetic pathway consistent with the genes in the cluster and the metabolites produced by S. antibioticus, and correspondingly different from that of S.?clavuligerus, is proposed.     

Reproductive biology and isolation mechanisms in rupicolous species of the Acianthera prolifera complex (Orchidaceae) occurring in southeastern Brazil

We studied the floral biology and performed experimental intra- and interspecific pollinations in populations of a complex of four Acianthera (Orchidaceae) species occurring in Brazilian campo rupestre vegetation (A.?hamosa, A.?limae, A.?modestissima, and A.?prolifera). All four species flower synchronously, are partially intercompatible, and exhibited some degree of self-sterility. Floral morphology is similar in all the species, with their principal differences associated with size of the floral structures. The four species were visited only by Diptera species of the families Phoridae (Megaselia spp.) and Chloropidae, but visits are rare and fruit set is very low. Sympatric species were not pollinated by the same Diptera species. Acianthera hamosa and A.?modestissima have the smallest flowers, and no marked morphological differences between them were observed; they were both pollinated by very similar Megaselia species. Both prepollination barriers and postpollination events are important to maintaining the isolation of the species, functioning as overlapping filters that diminish the possibility of gene flow between them. However, putative hybrids between A.?prolifera and A.?limae have been found. Conversely, A.?hamosa and A.?modestissima, which are recognized only by vegetative characters that show high phenotypic plasticity, seem only to be isolated by geographical barriers, and they may actually constitute a single species or be sister species.     

Comparative genomics of Neisseria weaveri clarifies the taxonomy of this species and identifies genetic determinants that may be associated with virulence

A group of bacterial strains formerly known as CDC group M-5 are opportunistic pathogens to humans. In 1993, a name, Neisseria weaveri, was proposed by two independent studies to harbor CDC group M-5 strains, namely N.?weaveri Holmes et?al. 1993 and N.?weaveri Andersen et?al. 1993, with two different 'type' strains. However, no study has been conducted on to the relatedness of the two 'type' strains, although the close relationship of the two taxa has long been accepted unofficially. Formally, the status of the name N.?weaveri Andersen et?al. 1993 is illegitimate because it is a later homonym of N.?weaveri Holmes et?al., 1993; but the name of the strain is still validly published. In this study, we attempt to resolve the confusion caused by the apparent duplication of the species N.?weaveri (with different type strains) using whole genome shotgun sequencing. We also sought to gain insight into the genetic characteristics of N.?weaveri by conducting comparative genomics. On the basis of genomic similarities revealed through a comparative genomic study, we propose that N.?weaveri Andersen et?al. 1993 should be re-classified as a later heterotypic synonym of N.?weaveri Holmes et?al., 1993.     

Development of a PCR assay to detect the potential production of nivalenol in Fusarium poae

Fusarium species can produce mycotoxins, which can contaminate cereal-based food producing adverse effects for human and animal health. In recent years, the importance of Fusarium poae has increased within the Fusarium head blight complex. Fusarium poae is known to produce trichothecenes, especially nivalenol, a potent mycotoxin able to cause a variety of toxic effects. In this study, a specific primer pair was designed based on the tri7 gene to detect potential nivalenol-producing F.?poae isolates. A total of 125 F.?poae, four F.?cerealis, two F.?culmorum, one F.?langsethiae, one F.?sporotrichioides and seven F.?graminearum, plus F.?austroamericanum, F.?meridionale, F.?graminearum sensu stricto and F.?cortaderiae from the NRRL collection were analysed, and only F.?poae isolates gave a positive result for the presence of a 296-bp partial tri7 DNA fragment. Moreover, the primer set was tested from cereal seed samples where F.?poae and other Fusarium species with a negative result for the specific reaction ( F.?graminearum, F.?oxysporum, F.?chlamydosporum, F.?sporotrichioides, F.?equiseti and F.?acuminatum) were isolated, and the expected fragment was amplified. We developed a rapid and reliable PCR assay to detect potential nivalenol-producing F.?poae isolates.     

Effect of a Novel Podophage AB7-IBB2 on Acinetobacter baumannii Biofilm

Biofilm formation in Acinetobacter baumannii is a common cause of nosocomial infections in humans. Clinical devices and abiotic surfaces are important sites of colonization leading to formation of biofilms. Such infections are often resistant to multiple antibiotic therapies, and hence there is need for an effective mode of control. Herein, we describe the isolation, characterization of a new lytic bacteriophage of A.?baumannii and its effect on biofilm. The phage AB7-IBB2, with a genome size of about 170?kb was identified to be of family Podoviridae as revealed by transmission electron microscopy. It had an isometric head (35?nm) and a short tail (7?nm). It lysed 19/39 (49?%) clinical isolates of A.?baumannii. Rapid adsorption (>99?% adsorbed in 4?min), a latency period of 25?min and a burst size 22?PFU/infected cell was observed. The phage could inhibit A.?baumannii biofilm formation and disrupt preformed biofilm as well. The phage has promising potential to be considered as a candidate biocontrol agent for A.?baumannii infections.     

Overexpression of serine hydroxymethyltransferase from halotolerant cyanobacterium in Escherichia coli results in increased accumulation of choline precursors and enhanced salinity tolerance

A real-time PCR procedure targeting the gene of the molecular cochaperon DnaJ (dnaJ) was developed for specific detection of strains belonging to the Enterobacter cloacae group. The inclusivity and exclusivity of the real-time PCR assay were assessed with seven reference strains of E.?cloacae, 12 other Enterobacter species and 41 non-Enterobacter strains. Inclusivity as well as exclusivity of the duplex real-time PCR was 100%. In contrast, resolution of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was inadequate for delineation of Enterobacter asburiae, Enterobacter hormaechei, Enterobacter kobei and Enterobacter ludwigii from E.?cloacae. Eleven of 56 (20%) clinical isolates of the E.?cloacae group could not be clearly identified as a certain species using MALDI-TOF MS. In summary, the combination of MALDI-TOF MS with the E.?cloacae-specific duplex real-time PCR is an appropriate method for identification of the six species of the E.?cloacae complex.     

In vitro propagation of Candidatus Rickettsia andeanae isolated from Amblyomma maculatum

Candidatus Rickettsia andeanae was identified during an investigation of a febrile outbreak in northwestern Peru (2002). DNA sequencing from two ticks (Amblyomma maculatum, Ixodes boliviensis) collected during the investigation revealed a novel Rickettsia agent with similarity to the spotted fever group rickettsiae. Since then, Candidatus R.?andeanae has been detected in A.?maculatum ticks collected in the southeastern and southcentral United States, Argentina, and Peru. To date, Candidatus R.?andeanae has not been successfully cultivated in the laboratory. We present evidence for the continuous cultivation in three cell lines of Candidatus R.?andeanae isolated from an A.?maculatum tick (Portsmouth, Virginia).     

Carbon isotopic composition of Ambrosia and Artemisia pollen: assessment of a C(3) -plant paleophysiological indicator

? There is limited evidence on how shifts in plant physiological performance influence vegetation variations in the paleorecord. ? To evaluate δ(13) C of pollen from C(3) plants as an indicator of community-level physiology, small quantities (10-30 grains) of untreated pollen and sporopollenin from herbarium specimens of Ambrosia (A.?tomentosa and A.?psilostachya) and Artemisia (A.?frigida, A.?ludoviciana and A.?dracunculus), genera abundant in grassland pollen profiles, were isolated by micromanipulation. Their δ(13) C values were measured using a spooling-wire microcombustion device interfaced with an isotope-ratio mass spectrometer. Leaf δ(13) C was also measured. Carbon isotope discrimination (Δ) for untreated pollen, sporopollenin and leaves was compared with historic records of seasonal precipitation amount, vapor pressure deficit and the Palmer Drought Severity Index (PDSI). ? Each species showed positive correlations between Δ of untreated pollen and sporopollenin. Sporopollenin Δ was most strongly correlated with PDSI. Correlations among leaf Δ and moisture indicators were stronger for Ambrosia than Artemisia. ? These results suggest that sporopollenin Δ indicates the level of moisture stress in C(3) plants. Therefore, δ(13) C analysis of pollen promises to help address important paleoecological questions, such as how community-level physiology contributes to shifts in vegetation composition.     

Production of a thermostable alcohol dehydrogenase from Rhodococcus ruber in three different yeast species using the Xplor?2 transformation/expression platform

The Xplor(?)2 transformation/expression platform was employed for comparative assessment of three different yeast species as hosts for synthesis of a thermostable nicotinamide adenine dinucleotide (NAD(+))-dependent medium-chain alcohol dehydrogenase from Rhodococcus ruber strain 219. Using yeast ribosomal DNA (rDNA) integrative expression cassettes (YRCs) and yeast integrative expression cassettes (YICs) equipped with a selection-marker module and one, two or four expression modules for transformation of auxotrophic Arxula adeninivorans, Hansenula polymorpha, and Saccharomyces cerevisiae strains, quantitative comparison of the yield of recombinant alcohol dehydrogenase RR-ADH6Hp in all three species was carried out. In all cases, the RR-ADH6H gene was expressed under the control of the strong constitutive A.?adeninivorans-derived TEF1 promoter, which functions in all yeast species analyzed. Recombinant RR-ADH6Hp accumulated intracellularly in all strains tested. The best yields of active enzyme were obtained from A.?adeninivorans, with S.?cerevisiae producing intermediate amounts. Although H.?polymorpha was the least efficient producer overall, the product obtained was most similar to the enzyme synthesized by R.?ruber 219 with respect to its thermostability.     

Persistence of Escherichia coli in freshwater periphyton: biofilm-forming capacity as a selective advantage

Recent research has shown that Escherichia coli can persist in aquatic environments, although the characteristics that contribute to their survival remain poorly understood. This study examines periphytic E.?coli populations that were continuously present in three temperate freshwater lakes from June to October 2008 in numbers ranging from 2 to 2?×?10(2) CFU?100?cm(-2) . A crystal violet assay revealed that all tested periphytic E.?coli isolates were superior biofilm formers and they formed, on average, 2.5 times as much biofilm as E.?coli isolated from humans, 4.5 times as much biofilm as shiga-like toxin-producing E.?coli, and 7.5 times as much biofilm as bovine E.?coli isolates. Repetitive extragenic palindromic polymerase chain reaction (REP-PCR) DNA fingerprinting analysis demonstrated the genetically diverse nature of the periphytic isolates, with genetic similarity between strains ranging from 40% to 86%. Additionally, the role of curli fibers in biofilm formation was investigated by comparing biofilm formation with curli expression under optimal conditions, although little correlation (R(2) =?0.095, P?=?0.005) was found. The high mean biofilm-forming capacity observed in E.?coli isolated from the periphyton suggests that selective pressures may favor E.?coli capable of forming biofilms in freshwater environments.     

Differential reproductive timing in Echinocardium spp.: the first Mediterranean survey allows interoceanic and interspecific comparisons

Echinocardium cordatum had long been considered as cosmopolitan, but molecular data revealed it is a complex of cryptic species, with two non-hybridizing species (B1 & B2) in the Mediterranean Sea living in syntopy with Echinocardium mediterraneum. Histological analyses of the gonads from a 17-month sampling period revealed a statistically significant time lag between the Maturity Indices of E.?cordatum and E.?mediterraneum. The main environmental stimulus may be different for the two nominal species, possibly seawater temperature for E.?cordatum and chlorophyll a concentration for E.?mediterraneum. Within the E.?cordatum complex, spawning timing and synchrony are different according to major geographic areas (Atlantic/Pacific/Mediterranean) and/or the corresponding genetic subdivision [A/P/(B1 & B2)]. In contrast, the effects of temperature on the reproductive cycle seem rather to mirror the genetic lineages than environmental similarities of the different localities. Between the sister species (B1 & B2) no differences could be detected, maybe due to small sample sizes.     

Genomic comparison of the endophyte Herbaspirillum seropedicae SmR1 and the phytopathogen Herbaspirillum rubrisubalbicans M1 by suppressive subtractive hybridization and partial genome sequencing

Herbaspirillum rubrisubalbicans M1 causes the mottled stripe disease in sugarcane cv. B-4362. Inoculation of this cultivar with Herbaspirillum seropedicae SmR1 does not produce disease symptoms. A comparison of the genomic sequences of these closely related species may permit a better understanding of contrasting phenotype such as endophytic association and pathogenic life style. To achieve this goal, we constructed suppressive subtractive hybridization (SSH) libraries to identify DNA fragments present in one species and absent in the other. In a parallel approach, partial genomic sequence from H.?rubrisubalbicans M1 was directly compared in silico with the H.?seropedicae SmR1 genome. The genomic differences between the two organisms revealed by SSH suggested that lipopolysaccharide and adhesins are potential molecular factors involved in the different phenotypic behavior. The cluster wss probably involved in cellulose biosynthesis was found in H.?rubrisubalbicans M1. Expression of this gene cluster was increased in H.?rubrisubalbicans M1 cells attached to the surface of maize root, and knockout of wssD gene led to decrease in maize root surface attachment and endophytic colonization. The production of cellulose could be responsible for the maize attachment pattern of H.?rubrisubalbicans M1 that is capable of outcompeting H.?seropedicae SmR1.     

Broad diversity of conjugative plasmids in integron-carrying bacteria from wastewater environments

In this study we assessed the occurrence, diversity and conjugative potential of plasmids in integron-carrying Aeromonas and Enterobacteriaceae from wastewaters. Sixty-six strains were included as donors in mating assays using rifampicin-resistant Escherichia coli and Pseudomonas putida recipient strains. The diversity of plasmids from donors and transconjugants (resistant to tetracycline or streptomycin) was evaluated by restriction analysis and replicon typing targeting 19 incompatibility groups. Restriction patterns revealed a diverse plasmid pool present in these strains. Plasmids were assigned to FrepB (Aeromonas salmonicida, Aeromonas veronii, Aeromonas sp., E.?coli, Enterobacter sp.), FIC (A.?salmonicida, Aeromonas sp.), FIA (Shigella sp.), I1 (A.?veronii, Aeromonas sp., E.?coli), HI1 (E.?coli) and U (Aeromonas media) replicons. Nevertheless, 50% of the plasmids could not be assigned to any replicon type. Among integron-positive transconjugants, FrepB, I1 and HI1 replicons were detected. Results showed that wastewaters enclose a rich plasmid pool associated with integron-carrying bacteria, capable of conjugating to different bacterial hosts. Moreover, replicons detected in this study in Aeromonas strains expand our current knowledge of plasmid diversity in this genus.     

Cloning and partial characterization of a novel hemolysin gene of Vibrio tubiashii and the development of a PCR-based detection assay

Vibrio tubiashii expresses virulence factors, such as a vulnificolysin-like hemolysin or cytolysin and a zinc metalloprotease, similar to those of other pathogenic vibrios. In this study, we report the cloning of a novel hemolysin gene of V.?tubiashii in Escherichia coli . A V.?tubiashii gene library was screened for hemolytic activity on sheep blood agar. Three hemolytic clones pGem:hly1, pGem:hly2, and pGem:hly3 were sequenced, and the sequences showed a strong homology to the ribA gene coding for guanosine triphosphate cyclohydrolase II (GCH II), required for riboflavin biosynthesis and reported to be responsible for hemolytic activity in Helicobacter pylori . The plasmids pGem:hly1 and pGem:hly3 when introduced into E. coli BSV18 (ribA18::Tn5) were able to restore growth of strain BSV18 in a medium without riboflavin and also produced hemolytic activity on blood agar. PCR primers based on the cloned hly-ribA sequence were tested using 23 different Vibrio strains representing 10 different species. Amplification of ribA gene locus only occurred with V.?tubiashii strains. In summary, our results indicate that we have cloned a ribA homolog of V.?tubiashii that imparts hemolytic activity to E.?coli clones, and primers based on this gene locus might be useful as a species-specific identification tool for V.?tubiashii.     

Asymmetric reproductive interference between specialist and generalist predatory ladybirds

1.?Closely related species often differ greatly in the quality and breadth of resources exploited, but the actual mechanisms causing these differences are poorly understood. Because in the laboratory specialized species often survive and perform as well or better on host species that are never utilized in nature, negative ecological interactions restricting host range must exist. Here, we focused on reproductive interference, which has been theoretically predicted to drive niche separation between closely related species with overlapping mating signals. 2.?We examined the interspecific sexual interactions in relation to ecological specialization and generalization in two sibling ladybird species, Harmonia yedoensis and Harmonia axyridis. Harmonia yedoensis is a specialist predator that preys only on pine aphids, which are highly elusive prey for ladybird hatchlings, whereas H.?axyridis is a generalist predator with a broad prey and habitat range. 3.?We experimentally showed that conspecific sperm fertilized the vast majority of eggs regardless of mating order (i.e. conspecific sperm precedence) when a female of H.?yedoensis or H.?axyridis mated with both a conspecific and a heterospecific male. Moreover, we demonstrated that mating opportunities of H.?yedoensis females strongly decreased as heterospecific density increased relative to conspecific density. In contrast, in H.?axyridis, female mating success was high regardless of conspecific or heterospecific density. 4.?Our results suggest that the generalist H.?axyridis should be dominant to the specialist H.?yedoensis in terms of reproductive interference. Our results support the hypothesis that asymmetric reproductive interference from the dominant species may force the non-dominant species to become a specialist predator that exclusively utilizes less preferred prey in nature.