Effects of predation risk on population variation in adult size in a stream-dwelling isopod

I used a combination of laboratory experiments and field surveys to examine the role that population-specific predation risk may play in shaping the life history strategy of a stream-dwelling isopod Lirceus fontinalis. Two focal populations were identified that were exposed to different predator types. The first population was exposed to larvae of the streamside salamander (Ambystoma barbouri) and the second to banded sculpin (Cottus carolinae). A laboratory experiment, in which different size classes of prey were offered simultaneously to individual predators, revealed that L. fontinalis suffered greatest mortality risk at small sizes with A. barbouri. Alternatively, with C. carolinae the risk of mortality was independent of size. Life history theory predicts that L. fontinalis from populations exposed to the gape-limited salamander larvae should be larger at maturity relative to individuals from populations exposed to C. carolinae. Field surveys on the two focal populations both within 1 year and across 4 years supported this prediction. Four other populations, two exposed to streamside salamander larvae and two to fish, provided additional support for the prediction. I concluded that L. fontinalis exhibited an adaptive response in size at maturity in response to population-specific predation risk. I then used gut content assays of the major predators to assess whether the population-specific life history strategies adopted by L. fontinalis were successful in avoiding predation.     

INTRASPECIFIC PHYLOGEOGRAPHY OF NORTH AMERICAN HIGHLAND FISHES: A TEST OF THE PLEISTOCENE VICARIANCE HYPOTHESIS

The highland fish fauna of eastern North America consists of Appalachian and Ozark centers of endemism separated by the intervening Glacial Till Plains. Clades within these areas are more closely related phylogenetically to each other than to clades occurring in the intervening formerly glaciated region, suggesting that the Pleistocene glaciations fragmented a widespread highland region and its associated fauna. Alternatively, it is possible that these faunal assemblages predate the glaciations or that recent dispersals may have been more important than vicariance in determining faunal compositions. We examined the relationships among mitochondrial DNA (mtDNA) haplotypes within five clades of highland fishes, each with a distribution suggestive of a Pleistocene vicariance event. Darters of the subgenera Litocara and Odontopholis have distributions and mtDNA relationships that are consistent with the Pleistocene integration and burial of the Teays-Mahomet valley, a major drainage of the early Pleistocene. The distribution and mtDNA relationships among subspecies of Erimystax dissimilis are not consistent with Pleistocene vicariance, but relationships among Appalachian haplotypes are consistent with the late Pleistocene integration of the modern Ohio River system. Both Cottus carolinae and the Fundulus catenatus species group have representatives in the Mobile basin consistent with pre-Pleistocene divergences. Three haplotype clusters were found in C. carolinae, corresponding to the Appalachian, Ozark, and upper Kanawha River populations. However, Appalachian and Ozark F. catenatus populations are paraphyletic with respect to each other. This, coupled with a relatively low degree of sequence divergence, suggests that no long-term barriers to gene flow exist for C. carolinae and F. catenatus. These three distinct phylogeographic patterns indicate that Pleistocene vicariance is not the only explanation for the Appalachian-Ozark distribution of highland fish communities.     

Ecomorphology and habitat utilization of Cottus species

We investigated relationships between morphological attributes and mesohabitat use in populations of Cottus carolinae. Field studies revealed significant differences between Ozark and prairie stream mesohabitats where populations of C. carolinae occurred. Features of the mesohabitat that were characteristic of each stream type correlated with intra- and inter-specific differences in morphological attributes of Cottus. The morphology of Cottus occurring in the deeper, slower, and siltier prairie stream exhibited larger head width and depth, body width and depth, and caudal peduncle width while those occurring in a shallower, faster flowing Ozark stream had longer pelvic fins, larger eyes, and deeper caudal peduncles. Each population had a morphology tailored to optimize its performance in a specific habitat. Results of laboratory based performance studies using a variable flow chamber revealed that critical current velocities (CCV) of live and preserved specimens were weakly associated with distinct combinations of morphological traits. Specimens with higher CCV measurements typically had longer pelvic fins, larger eyes, and deeper caudal fins (Ozark morphology). Those with lower CCVs had larger head width and depth, body width and depth, and caudal peduncle width (prairie morphology) in studies using cobble as the substrate. Differences in flow regimes between prairie and Ozark streams may generate specific niches for specific morphotypes, and current velocity may exert selective pressure on morphology.     

Biotransformation of pseudolaric acid B by Chaetomium globosum

Pseudolaric acid B (1) is a natural product with potent antifungal activity. We discovered that pseudolaric acid B did not kill but only suppress the growth of the filamentous fungus Chaetomium globosum. It was proposed that pseudolaric acid B was converted to metabolites with decreased antifungal activities. In this study, a scaled-up biotransformation of pseudolaric acid B by C. globosum produced five metabolites, including three new compounds, pseudolaric acid I (2), pseudolaric acid B 18-oyl-alanine (4) and pseudolaric acid B 18-oyl-serine (6), together with two known compounds, pseudolaric acid F (3) and pseudolaric acid B 18-oyl-glycine (5). The structures were characterized by NMR and MS spectroscopy. The major biotransformation reaction was conjugation with amino acids. None of the metabolites showed inhibitory effects on the growth of Candida albicans. The results suggested that biotransformation might be a detoxification process for fungi to resist antifungal drugs.     

Morphological,ecological and molecular studies of the intergrading taxa Bryum neodamense and B. pseudotriquetrum (Bryopsida: Bryaceae)

Abstract

Studies of Bryum neodamense at most of its localities in the British Isles revealed that plants with morphology intermediate with B. pseudotriquetrum var. pseudotriquetrum frequently accompany B. neodamense. A survey of herbarium specimens found that similar intermediates are widespread in continental Europe and also occur in Asia, Alaska and Greenland. Phylogenetic analyses of DNA sequences from three loci imply that B. neodamense and intermediate plants are nested within the rather variable B. pseudotriquetrum. It is therefore concluded that, despite its striking morphological characters, B. neodamense is an inconstant phenotype of B. pseudotriquetrum, which occurs very locally in highly calcareous habitats that are subject to periodic inundation.     

A Lichenological Excursion to the West of Scotland

ABSTRACT

Background: Hybridisation can be a threat for the survival of a rare species because, in the case of insufficient numbers of appropriate mates, a rare form is much more likely to cross with a widespread taxon.

Aims: In the present study, we tested hypotheses concerning the level of hybridisation between endangered Betula humilis and its widespread congeners: B. pendula and B. pubescens as a function of habitat conditions.

Methods: We genotyped 312 individuals of three species using AFLP markers. B. humilis specimens were sampled in populations with low and high groundwater levels. Morphological identification of B. pubescens and B. pendula was verified using the Atkinson discriminant function.

Results: Altogether, 15 individuals (4.8%) were indicated as putative hybrids. The B. humilis hybrids were found in dry habitats and they could be classified as F1 or F2 generation. Tree hybrids could represent backcrosses to either B. pendula or B. pubescens.

Conclusions: Genetic analyses contradicted the idea that hybridisation between B. humilis and its close relatives was extensive. On the other hand, the presence of introgressed individuals in the populations in areas with low groundwater levels implied that pollen swamping might be a threat for declining B. humilis stands.     

Assessing riverscape-scale variation in fish life history using banded sculpin (<Emphasis Type="Italic">Cottus carolinae</Emphasis>)

Advancing the field of fish ecology requires a shift in focus from describing patterns in species occurrences to understanding the mechanisms that regulate distributions and abundances across broad scales. For stream fish ecology, this includes understanding environmental mechanisms that regulate stream fish demographic properties at the scale of stream networks or riverscapes. Despite the fact that Banded Sculpin Cottus carolinae occupy a diversity of habitats and stream sizes across the southeastern United States, relatively little is known about the demography of this species. We assessed annual demographic properties (reproduction, growth, and survival) of C. carolinae collected monthly from four sites distributed longitudinally along the Roaring River riverscape in Tennessee to simultaneously describe life history attributes of the species and address riverscape-scale variation in population dynamics. Cottus carolinae lived for a maximum of four years, local populations were dominated by age-0 and age-1 individuals, reproduction began after one year, spawning occurred during December and January, and mean ova number was 398. A life history tradeoff between growth (robustness) and survival was evident at one site where water temperature and flow were least variable, otherwise life history attributes were consistent across the riverscape despite longitudinal changes in abiotic variables. Our work illustrates the potential for muted population responses to a strong hydrologic gradient in stream size and highlights the stability inherent with fish life history adaptations to natural environmental regimes across broad spatial scales.     

Novelties in spermacoceae (Rubiaceae) from Bolivia and Paraguay

One new Bolivian species (Borreria pazensis) and three new varieties (Borreria densiflora var.minima, Richardia, scabra var.chacoensis andStaelia virgata var.killeenii) are described and illustrated. The genusDiodella, with three species (D. apiculata comb. nov., D. radula comb. nov., andD. teres), is reported for the first time.Borreria limae, B. wunschmannii, B. scabiosoides var.scabiosoides, andB. scabiosoides var.anderssonii are also reported as new to Bolivia.     

Two new species of Blechnum (Blechnaceae) from the neotropics

Blechnum moranianum is a new species similar toB. loxense, andB. nigrum is segregated from theB. fragile complex. Both are described and illustrated as result of the author's taxonomic fern work in Costa Rica. Blechnum moranianum es una especie nueva similar aB. loxense, yB. nigrum es segregada del complejoB. fragile. Ambas son aquí descritas e ilustradas como resultado de los trabajos taxonómicos del autor en los helechos de Costa Rica.     

PTP1B inhibitory activity of kaurane diterpenes isolated from Siegesbeckia glabrescens

Protein tyrosine phosphatase 1B (PTP1B) is considered as a therapeutic target for the treatment of diabetes and obesity. In our preliminary screening study, a MeOH extract of the aerial part of Siegesbeckia glabrescens was found to inhibit PTP1B activity at 30 μg/mL. Bioassay‐guided fractionation led to the isolation of two active diterpenes, ent-16βH,17-isobutyryloxy-kauran-19-oic acid (1) and ent-16βH,17-acetoxy-18-isobutyryloxy-kauran-19-oic acid (2), along with ent-16βH,17-hydroxy-kauran-19-oic acid (3). Compounds 1 and 2 inhibited the PTP1B activity with IC₅₀ values of 8.7 ± 0.9 and 30.6 ± 2.1 μM, respectively. Kinetic studies suggest that both 1 and 2 are non-competitive inhibitors of PTP1B. However, compound 3 substituted with a hydroxyl group at C-17 in kaurane-type showed no inhibitory effects towards PTP1B.     

Differences in investment and functioning of cluster roots account for different distributions of Banksia attenuata and B. sessilis,with contrasting life history

Aims

Banksia attenuata is a resprouting species growing in deep sand, while B. sessilis is a fire-killed species occurring in shallow sand over laterite or limestone. We aimed to discover the ecophysiological basis for their different distributions by exploring their investment in deep non-cluster roots and shallow cluster roots, and their cluster-root functioning.

Methods

Deep-pot (1 m), shallow-pot (400 mm), hydroponic experiments and phosphorus (P)-extraction experiment were carried out. Biomass allocation, cluster-root exudation, plant P and leaf manganese (Mn) concentrations were measured.

Results

Banksia attenuata allocated more biomass to deep roots and less biomass to cluster roots than B. sessilis did in deep pots. The two Banksias released similar carboxylates in all experiments, with similar carboxylate-exudation rates in hydroponics. The carboxylate amount per unit cluster root of B. sessilis grown in shallow pots was greater than that of B. attenuata, and B, sessilis acquired more P than B. attenuata did in limestone substrate.

Conclusions

Greater investment in deep roots for water uptake accounts for the presence of B. attenuata in deep sand, and vice versa for the absence of B. sessilis. A larger investment in cluster roots, which released greater amounts of carboxylates, likely accounts for B. sessilis occurring over limestone. Trade-offs in investment and cluster-root functioning support the species’ distribution patterns and life histories. Leaf Mn concentration was a good proxy for the plant capacity to acquire P.

     

小肠结肠炎耶尔森菌对多粘菌素B的压力应答

【背景】小肠结肠炎耶尔森菌(Yersinia enterocolitica)是重要的人畜共患食源性病原菌。由于其生存环境与传染性生活方式,小肠结肠炎耶尔森菌暴露在各种生存压力中,而胞膜压力应答能力对维持其环境耐受性和毒力发挥着重要作用。【目的】探究小肠结肠炎耶尔森菌在胞膜压力应答中的调节机制。【方法】通过使用多粘菌素B破坏小肠结肠炎耶尔森菌细胞膜的稳定性,并从生长能力、运动能力、生物被膜形成能力以及相关基因表达的变化探讨Rcs (Regulator of Capsule Synthesis)系统对多粘菌素B产生的胞膜压力的应答。【结果】多粘菌素B引起的细胞胞膜压力抑制了小肠结肠炎耶尔森菌的运动和生物被膜形成能力;而阻断Rcs信号途径后,小肠结肠炎耶尔森菌的运动和生物被膜形成能力有所恢复。对flhC、hmsS、hmsT等关键下游表型基因的表达水平的分析结果表明Rcs双组分系统对由多粘菌素B诱导的胞膜压力作出响应,通过感知胞膜胁迫向胞内传递信号,积极地调控细菌增强对抗菌肽的抗性。【结论】明确了Rcs双组分系统在响应多粘菌素B压力胁迫中的特异性调控作用,加深了对小肠结肠炎耶尔森菌环境应答机制...     

A new combination in Pseudosymblepharis (Pottiaceae) from South and Central America

Abstract

Trichostomum schlimii Müll.Hal., a neglected Colombian taxon, is transferred to the genus Pseudosymblepharis Broth. as Pseudosymblepharis schlimii (Müll.Hal.) comb. nov. The species, known only from the type locality in Santa Marta, Colombia, is newly reported for the moss floras of Bolivia, Brazil, Dominican Republic, Ecuador, Guiana, Peru, and Venezuela. It is described, lectotypified, illustrated, and mapped. Diagnostic characters, and distinction from one closely related American species within the genus are discussed. Trichostomum mollissimum (Broth. ex E.B.Bartram) H.A.Crum and Pseudosymblepharis guatemalensis (E.B.Bartram) B.H.Allen are reduced to the synonymy of Pseudosymblepharis schlimii.     

Hypolipidemic and anti-inflammatory properties of phenolic rich Butia odorata fruit extract: potential involvement of paraoxonase activity

Abstract

Aim: This study investigated the effects of polar Butia odorata fruit extract on metabolic, inflammatory, and oxidative stress parameters in rats submitted to a hyperlipidaemia condition induced by tyloxapol.

Methods: Animals were divided into 3 groups: saline, saline plus tyloxapol, and B. odorata extract plus tyloxapol. Animals were treated for 15?days with a saline solution or B. odorata fruit extract and after hyperlipidaemia was induced by tyloxapol.

Results: Treatment with B. odorata extract reduced serum triglyceride, total cholesterol, C-reactive protein, and adenosine deaminase and butyrylcholinesterase activities when compared to the tyloxapol group. HDL-cholesterol and paraoxonase 1 activity were higher in B. odorata extract treated animals when compared to tyloxapol-treated animals. No differences were observed in hepatic oxidative stress parameters. Phenolic compounds present in B. odorata fruit extract were identified and quantified by LC-MS/MS.

Conclusion: These findings indicated that phenolic rich B. odorata extract has hypolipidemic and anti-inflammatory effects in hyperlipidemic rats.     

Brassica glabrescens,eine neue Art aus Nordost-Italien

Abstract

The new endemic species Brassica glabrescens Poldini is described from the Friuli, Italy. It is a perennial caespitose hemicryptophyte belonging to sect. Brassicaria (Godr.) Coss. (= Oreobrassica Prantl), which shows close affinity to the very complex species B. repanda (Willd.) DC. and particularly to its subsp. saxatilis (DC.) Heywood from South France.     

Blechnum obtusum (Blechnaceae), a new species from western Venezuela

Blechnum obtusum is described and illustrated as a new species. It grows in páramos of western Venezuela and most resemblesB. werffii of Costa Rica and Panama.     

地衣芽孢杆菌对南美白对虾零水交换养殖系统细菌群落的影响

【目的】地衣芽孢杆菌（Bacillus licheniformis）对南美白对虾（Penaeus vannamei）免疫反应、抗病性和营养的影响已被广泛研究，但零水交换养殖系统下地衣芽孢杆菌对对虾肠道和养殖水环境微生物群落的影响尚不清楚。【方法】通过收集添加地衣芽孢杆菌在饲料或水中后，对虾肠道、池水和池低沉积物样品，通过16S rRNA基因测序和线性判别分析（linear discriminant analysis effect size，LEfSe）进行微生物分析。【结果】结果表明，添加地衣芽孢杆菌对对虾的生长影响较小。此外，添加方式的不同对对虾肠道菌群的影响较小。但添加地衣芽孢杆菌可以有效地改变对虾肠道微生物群落，并改善对虾免疫力。【结论】这些结果有助于全面了解在零水交换养殖系统中，通过饲料和水添加地衣芽孢杆菌后对虾肠道和环境的变化，从而为选择正确的益生菌以及如何添加益生菌维持对虾健康提供基础信息。     

The taxonomic position of Oxystegus sinuosus (Mitt.) Hlip. in relation to the genus Barbula Hedw

Abstract

The morphology of leaves, stems and axillary hairs is compared and described in Oxystegus sinuosus and O. tenuirostris. It is suggested that O. sinuosus falls within the range of variation of Barbula as currently understood in Britain, but that O. tenuirostris is closer to Trichostomum. The morphology of the axillary hairs does not throw much light on its affinities within Barbula, but a position close to B. cylindrica is probably the most appropriate.     

日化产品中洋葱伯克霍尔德氏菌复合群(Bcc)的分类和神秘伯克霍尔德氏菌的耐药性研究

【目的】对从2020–2022年不同日化产品中分离的29株洋葱伯克霍尔德氏菌复合群(Burkholderia cepacia complex,Bcc)进行分类和分型,另将2020年前来源于日化产品中6株被鉴定为Burkholderia lata的菌株进行分类更正。探究神秘伯克霍尔德氏菌(Burkholderia aenigmatica)的耐药性。【方法】本文主要应用多位点分型研究方法(multilocus sequence typing,MLST),PCR扩增atpD、gltB、gyrB、recA、lepA、phaC和trp B 7个管家基因片段,将测序结果与MLST数据库中的数据比对分析,获得菌株各管家基因的编号和ST型(sequence type),对本检测中心分离自日化产品的Bcc进行分型;利用多位点序列分析(multilocus sequence analysis,MLSA),结合MLST中等位基因的核苷酸序列构建进化树,从而对Bcc进行系统发育分析和鉴定。利用最小抑菌浓度法(minimum inhibitory concentration,MIC)测定Bcc对常见防腐剂(1,...     

Virtual screening of LPXTG competitive SrtA inhibitors targeting signal transduction mechanism in Bacillus anthracis: a combined experimental and theoretical study

Abstract

Members of the sortase enzyme super family decorate the surfaces of Bacillus anthracis cell wall with proteins that play key roles in microbial pathogenesis and its biofilm formation. Bacillus anthracis Sortase-A (Ba-SrtA) is a potential target for new therapeutics as it is required for B. anthracis survival and replication within macrophages. An understanding of the binding site pocket and substrate recognition mechanism by SrtA enzymes may serve to be beneficial in the rational development of sortase inhibitors. Here, the LPXTG signal peptide-based competitive inhibitors are screened against the Ba-SrtA and compounds with reasonable inhibition, specificity, and mechanisms of inactivation of SrtA have been covered. The screened compounds are experimentally validated against the phylogenetically similar Gram-positive pathogen B. cereus. In situ microscopic visualizations suggest that these screened compounds showed the microbial and biofilm inhibitory activity against B. cereus. It facilitates the further development of these molecules into useful anti-infective agents to treat infections caused by B. anthracis and other Gram-positive pathogens. These results provide insight into basic design principles for generating new clinically relevant lead molecules. It also provides an alternative strategy where a screened ligand molecule can be used in combination to battle increasingly against the Gram-positive pathogens.