Cloning of the unculturable parasite Pasteuria ramosa and its Daphnia host reveals extreme genotype-genotype interactions

The degree of specificity in host-parasite interactions has important implications for ecology and evolution. Unfortunately, specificity can be difficult to determine when parasites cannot be cultured. In such cases, studies often use isolates of unknown genetic composition, which may lead to an underestimation of specificity. We obtained the first clones of the unculturable bacterium Pasteuria ramosa, a parasite of Daphnia magna. Clonal genotypes of the parasite exhibited much more specific interactions with host genotypes than previous studies using isolates. Clones of P. ramosa infected fewer D. magna genotypes than isolates and host clones were either fully susceptible or fully resistant to the parasite. Our finding enhances our understanding of the evolution of virulence and coevolutionary dynamics in this system. We recommend caution when using P. ramosa isolates as the presence of multiple genotypes may influence the outcome and interpretation of some experiments.     

Myomegalin is a novel A-kinase anchoring protein involved in the phosphorylation of cardiac myosin binding protein C

Background  

Cardiac contractility is regulated by dynamic phosphorylation of sarcomeric proteins by kinases such as cAMP-activated protein kinase A (PKA). Efficient phosphorylation requires that PKA be anchored close to its targets by A-kinase anchoring proteins (AKAPs). Cardiac Myosin Binding Protein-C (cMyBPC) and cardiac troponin I (cTNI) are hypertrophic cardiomyopathy (HCM)-causing sarcomeric proteins which regulate contractility in response to PKA phosphorylation.     

Survey of <Emphasis Type="Italic">Wolbachia</Emphasis> and Its Phage WO in the Uzifly <Emphasis Type="Italic">Exorista sorbillans</Emphasis> (Diptera: Tachinidae)

Wolbachia are cytoplasmically inherited alpha-proteobacteria well known for inducing a variety of reproductive abnormalities in the diverse arthropod hosts they infect. Despite their obligate intracellular lifestyle which usually protects bacteria from phage infection, Wolbachia harbor a widespread temperate phage called WO. Evidences of horizontal phage transfers indicate that this phage could promote genetic exchanges between strains leading to evolutionary changes in the genomes of Wolbachia, and could be involved in the phenotypes these bacteria induced. In this study, we report the survey of Wolbachia and WO phage infections in 20 populations of the Uzifly Exorista sorbillans, a tachinid endoparasite of silkworm Bombyx mori, collected from different geographic regions of India. Previous studies demonstrated that Wolbachia is associated with positive reproductive fitness effects in this species. Polymerase chain reaction using the ftsZ gene encoding for a Wolbachia cell division protein and the orf7 capsid protein gene of the phage showed that all flies checked were infected by Wolbachia and its phage WO. Phylogenetic analyses based on the Wolbachia surface protein gene revealed 100% of double infections by the arthropod supergroups A and B. These results can serve as a valuable basis for understanding the evolution of Wolbachia bacteria and may provide information about the dynamics of Wolbachia–host associations. This knowledge could be exploited for the use of Wolbachia for effective control strategies of the Uzifly, a serious menace of the silkworm B. mori.     

Variable-number tandem repeats as molecular markers for biotypes of Pasteuria ramosa in Daphnia spp

Variable-number tandem repeats (VNTRs) have been identified in populations of Pasteuria ramosa, a castrating endobacterium of Daphnia species. The allelic polymorphisms at 14 loci in laboratory and geographically diverse soil samples showed that VNTRs may serve as biomarkers for the genetic characterization of P. ramosa isolates.     

Variable-Number Tandem Repeats as Molecular Markers for Biotypes of Pasteuria ramosa in Daphnia spp.

Variable-number tandem repeats (VNTRs) have been identified in populations of Pasteuria ramosa, a castrating endobacterium of Daphnia species. The allelic polymorphisms at 14 loci in laboratory and geographically diverse soil samples showed that VNTRs may serve as biomarkers for the genetic characterization of P. ramosa isolates.     

Legitimation code theory to facilitate transition from high school to first-year biology

Institutions of Higher Education have grappled with the predicament of first-year success and epistemological access for years. Recently, a study employed Legitimation Code Theory (LCT) to elucidate why students who performed relatively well in high school biology struggled with the subject in first-year. This study shed valuable light on this problem by revealing that the high school biology curriculum is at a completely different level to the university curriculum. In terms of LCT’s Semantics dimension, the high school curriculum displayed little movement from context dependent simpler meanings towards the relatively decontextualised complex meanings, frequently encountered in first-year biology. We argue that the Semantics dimension of LCT also offers a useful tool for restructuring first-year biology curricula to intentionally facilitate a more gradual transition for first-year students. Thus, by explicitly planning teaching activities to gradually increase the range between context dependent simpler meanings and relatively decontextualized complex meanings, the potential of cumulative learning can be optimised. This paper reflects on the process of revising a first-year biology curriculum to contribute to greater epistemological access and cumulative knowledge building.     

Symbiotic interactions of culturable microbes with the nickel hyperaccumulator Berkheya coddii and the herbivorous insect Chrysolina clathrata

Chrysolina clathrata is a specialized phytophagous beetle feeding exclusively on the herbaceous nickel hyperaccumulating plant Berkheya coddii. These organisms appear impervious to the toxic levels of nickel in their environment. In the current study we aimed to identify microorganisms that may have symbiotic relationships with these organisms. Culture techniques were used to isolate bacteria and fungi from plants and the faeces of beetles reared under laboratory conditions. The identity of isolates was determined using morphology and molecular techniques. Several genera of filamentous fungi (Alternaria, Aspergillus, Bipolaris, Cladosporium, Epicoccum, Fusarium, and Penicillium), yeasts (Cryptococcus, Meyerozyma, and Rhodotorula), as well as endophytic bacteria (Bacillus and Lysinibacillus) were isolated from the leaves of the plant. We also selectively isolated yeasts (Candida, Cryptococcus, Debaryomyces, Meyerozyma and Wickerhamomyces) from the beetle’s faeces. Subsequently we determined the minimum inhibitory Ni-concentration (MIC) of all isolates. The endophytic bacteria, filamentous fungi and the yeasts Candida intermedia, Cryptococcus flavescens and Meyerozyma guilliermondii, showed notable Ni resistance, while the beetle’s gut seems to select for Ni resistant yeasts.     

Population genetic structure and secondary endosymbionts of Q Bemisia tabaci (Hemiptera: Aleyrodidae) from Greece

We investigated the molecular diversity of the major agricultural pest Bemisia tabaci and of its associated secondary endosymbionts in Greece. Analyzing mitochondrial DNA, we found that the Q1 (=Q west) is predominant. We used eight microsatellite polymorphic markers to study the genetic structure of 37 populations from mainland and insular Greece, collected on different host species from outdoor and protected crops as well as from non-cultivated plants. In some cases, gene flow was found to be low even between populations separated by just a few kilometres. Bayesian analysis identified two main genetic groups, the first encompassing populations from south Crete and the second composed of populations from north Crete, two other Aegean islands and mainland Greece. Genetic differentiation was not correlated with different host plant species or habitat, or greenhouse versus open environment populations. Gene flow significantly decreased with geographic distance, but no isolation by distance existed when only the samples from mainland Greece or only the samples from Crete were considered. The secondary symbionts Wolbachia and Hamiltonella were present at high frequencies while Arsenophonus, Cardinium and Rickettsia were absent from Greek populations. Multilocus sequence typing of Wolbachia identified two Wolbachia strains. These two strains were found together in most of the populations studied but never in the same host individual. Their role on the observed population structure is discussed.     

High-resolution melting technology: a new tool for studying the Wolbachia endosymbiont diversity in the field

Stable infections by maternally transmitted symbionts are frequently found in field populations, especially in arthropods. Many questions remain regarding their contribution to host biology and ecology, and especially on environmental adaptation of their host. Wolbachia is one of the most common endosymbiont of invertebrates. This cytoplasmically inherited endocellular bacterium induces number of reproductive alterations in its arthropod hosts and various fitness effects that allow it to spread in host populations. To better understand the influence of Wolbachia on host phenotypes and consequences of the manipulation of reproduction on the host genetic differentiation, it is crucial to be able to discriminate Wolbachia strains and determine their prevalence, which requires exhaustive screening. In the present report, we proposed the use of a new tool for the population studies, based on the high resolution melting (HRM) analysis, less expensive and faster than the 'classical' methods for large-scale studies. We investigated the effectiveness of HRM to explore and characterize the diversity of Wolbachia strains. Results obtained showed that HRM is a powerful tool to identify strains and detect polymorphism in singly infected hosts. When individuals harboured a mixture of Wolbachia strains (multiple infections), there is a risk of underestimation of the diversity if the proportions of the strains are highly different. However, the same limitations exist for the other techniques commonly used. Overall, this study demonstrated that HRM analysis is a rapid and reliable technique useful for studying, without a priori, Wolbachia strains diversity in field populations.