Hessian fly-associated bacteria: transmission, essentiality, and composition

Plant-feeding insects have been recently found to use microbes to manipulate host plant physiology and morphology. Gall midges are one of the largest groups of insects that manipulate host plants extensively. Hessian fly (HF, Mayetiola destructor) is an important pest of wheat and a model system for studying gall midges. To examine the role of bacteria in parasitism, a systematic analysis of bacteria associated with HF was performed for the first time. Diverse bacteria were found in different developmental HF stages. Fluorescent in situ hybridization detected a bacteriocyte-like structure in developing eggs. Bacterial DNA was also detected in eggs by PCR using primers targeted to different bacterial groups. These results indicated that HF hosted different types of bacteria that were maternally transmitted to the next generation. Eliminating bacteria from the insect with antibiotics resulted in high mortality of HF larvae, indicating that symbiotic bacteria are essential for the insect to survive on wheat seedlings. A preliminary survey identified various types of bacteria associated with different HF stages, including the genera Enterobacter, Pantoea, Stenotrophomonas, Pseudomonas, Bacillus, Ochrobactrum, Acinetobacter, Alcaligenes, Nitrosomonas, Arcanobacterium, Microbacterium, Paenibacillus, and Klebsiella. Similar bacteria were also found specifically in HF-infested susceptible wheat, suggesting that HF larvae had either transmitted bacteria into plant tissue or brought secondary infection of bacteria to the wheat host. The bacteria associated with wheat seedlings may play an essential role in the wheat-HF interaction.     

Linking Molecular Microbial Ecology to Geochemistry in a Coastal Hypoxic Zone

Multiple environmental mechanisms have been proposed to control bottom water hypoxia (<2 mg O₂ L^?1) in the northern Gulf of Mexico Louisiana shelf. Near-bottom hypoxia has been attributed to a direct consumption of oxygen through benthic microbial respiration and a secondary chemical reaction between oxygen and reduced metabolites (i.e. ferrous iron and total sulfide) from these populations. No studies to date have examined the metabolically active microbial community structure in conjunction with the geochemical profile in these sediments. Temporal and spatial differences in dissolved and solid phase geochemistry were investigated in the upper 20 cm of the sediment column. Pyrosequencing of reverse transcribed small subunit (SSU) ribosomal ribonucleic acid (rRNA) was used to determine population distribution. Results indicated that populations shallower than 10 cm below surface were temporally variable yet uniform between sites, while below this depth, populations were more site-specific. This suggests a potential interaction between the water column and the benthic microbial population limited to a shallow depth. The presence of dissolved reduced iron in the upper sediment column was indicative of low oxygen concentration, yet sulfide was at or below detection limits. Putative sulfate and iron reducing and oxidizing populations were metabolically active at similar depths suggesting potential recycling of products. Results from this study indicate low carbon concentrations in the shallow sediments limit general metabolic activity, reducing the potential for microbial respiration. Supplemental materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the supplemental file.     

Isolation and ultrastructural characterization of squid synaptic vesicles

Synaptic vesicles contain a variety of proteins and lipids that mediate fusion with the pre-synaptic membrane. Although the structures of many synaptic vesicle proteins are known, an overall picture of how they are organized at the vesicle surface is lacking. In this paper, we describe a better method for the isolation of squid synaptic vesicles and characterize the results. For highly pure and intact synaptic vesicles from squid optic lobe, glycerol density gradient centrifugation was the key step. Different electron microscopic methods show that vesicle membrane surfaces are largely covered with structures corresponding to surface proteins. Each vesicle contains several stalked globular structures that extend from the vesicle surface and are consistent with the V-ATPase. BLAST search of a library of squid expressed sequence tags identifies 10 V-ATPase subunits, which are expressed in the squid stellate ganglia. Negative-stain tomography demonstrates directly that vesicles flatten during the drying step of negative staining, and furthermore shows details of individual vesicles and other proteins at the vesicle surface.     

Crowding of molecular motors determines microtubule depolymerization

The assembly and disassembly dynamics of microtubules (MTs) is tightly controlled by MT-associated proteins. Here, we investigate how plus-end-directed depolymerases of the kinesin-8 family regulate MT depolymerization dynamics. Using an individual-based model, we reproduce experimental findings. Moreover, crowding is identified as the key regulatory mechanism of depolymerization dynamics. Our analysis reveals two qualitatively distinct regimes. For motor densities above a particular threshold, a macroscopic traffic jam emerges at the plus-end and the MT dynamics become independent of the motor concentration. Below this threshold, microscopic traffic jams at the tip arise that cancel out the effect of the depolymerization kinetics such that the depolymerization speed is solely determined by the motor density. Because this density changes over the MT length, length-dependent regulation is possible. Remarkably, motor cooperativity affects only the end-residence time of depolymerases and not the depolymerization speed.     

How do elevated levels of testosterone affect the function of the human fallopian tube and fertility?—New insights

Excess testosterone levels affect up to 20% of the female population worldwide and are a key component in the pathogenesis of polycystic ovary syndrome. However, little is known about how excess testosterone affects the function of the human fallopian tube—the site of gamete transport, fertilization, and early embryogenesis. Therefore, this study aimed to characterize alterations caused by long‐term exposure to male testosterone levels. For this purpose, the Fallopian tubes of nine female‐to‐male transsexuals, who had been undergoing testosterone treatment for 1–3 years, were compared with the tubes of 19 cycling patients. In the ampulla, testosterone treatment resulted in extensive luminal accumulations of secretions and cell debris which caused ciliary clumping and luminal blockage. Additionally, the percentage of ciliated cells in the ampulla was significantly increased. Transsexual patients, who had had sexual intercourse before surgery, showed spermatozoa trapped in mucus. Finally, in the isthmus complete luminal collapse occurred. Our results imply that fertility in women with elevated levels of testosterone is altered by tubal luminal obstruction resulting in impaired gamete transport and survival.     

Global remodelling of cellular microenvironment due to loss of collagen VII

The mammalian cellular microenvironment is shaped by soluble factors and structural components, the extracellular matrix, providing physical support, regulating adhesion and signalling. A global, quantitative mass spectrometry strategy, combined with bioinformatics data processing, was developed to assess proteome differences in the microenvironment of primary human fibroblasts. We studied secreted proteins of fibroblasts from normal and pathologically altered skin and their post‐translational modifications. The influence of collagen VII, an important structural component, which is lost in genetic skin fragility, was used as model. Loss of collagen VII had a global impact on the cellular microenvironment and was associated with proteome alterations highly relevant for disease pathogenesis including decrease in basement membrane components, increase in dermal matrix proteins, TGF‐β and metalloproteases, but not higher protease activity. The definition of the proteome of fibroblast microenvironment and its plasticity in health and disease identified novel disease mechanisms and potential targets of intervention.     

A method for estimating population sex ratio for sage‐grouse using noninvasive genetic samples

Population sex ratio is an important metric for wildlife management and conservation, but estimates can be difficult to obtain, particularly for sexually monomorphic species or for species that differ in detection probability between the sexes. Noninvasive genetic sampling (NGS) using polymerase chain reaction (PCR) has become a common method for identifying sex from sources such as hair, feathers or faeces, and is a potential source for estimating sex ratio. If, however, PCR success is sex‐biased, naively using NGS could lead to a biased sex ratio estimator. We measured PCR success rates and error rates for amplifying the W and Z chromosomes from greater sage‐grouse (Centrocercus urophasianus) faecal samples, examined how success and error rates for sex identification changed in response to faecal sample exposure time, and used simulation models to evaluate precision and bias of three sex assignment criteria for estimating population sex ratio with variable sample sizes and levels of PCR replication. We found PCR success rates were higher for females than males and that choice of sex assignment criteria influenced the bias and precision of corresponding sex ratio estimates. Our simulations demonstrate the importance of considering the interplay between the sex bias of PCR success, number of genotyping replicates, sample size, true population sex ratio and accuracy of assignment rules for designing future studies. Our results suggest that using faecal DNA for estimating the sex ratio of sage‐grouse populations has great potential and, with minor adaptations and similar marker evaluations, should be applicable to numerous species.     

Electrical penetration graph analysis of the feeding behavior of soybean aphids on soybean cultivars with antibiosis

The soybean aphid, Aphis glycine Matsumura (Hemiptera: Aphididae), is a major pest of soybean. In the current study, we used the Electrical Penetration Graph technique to study feeding behavior of soybean aphids on antibiotic-resistant soybean lines KS1621, KS1613, and KS1642, and a susceptible soybean line, KS4202. We observed that soybean aphids spent significantly shorter periods of time in the sieve element phase but slightly more times in nonprobing phases in all three resistant lines than in the susceptible control. Our study suggests that resistance factors exist in the phloem of the resistant soybean lines, and that these lines may contain antixenosis in addition to antibiosis.     

Factors influencing survival of native and translocated mountain quail in Idaho and Washington

Understanding survival and cause-specific mortality of native and translocated animals can help biologists design more effective recovery programs. We estimated survival rates for 181 native mountain quail (Oreortyx pictus) in west-central Idaho from 1992 to 1996 and for 199 translocated mountain quail in western Idaho and eastern Washington in 2005 and 2006. Spring–summer survival of native birds over 4 yr ranged from 0.210 (SE = 0.116) to 0.799 (SE = 0.103) and fall–winter survival in 2 yr was 0.523 (SE = 0.089) and 0.244 (SE = 0.084). Annual survival rates were 0.418 (SE = 0.088) and 0.174 (SE = 0.065). Spring–summer survival rate of translocated birds was 0.215 (SE = 0.044) in 2005 and 0.059 (SE = 0.021) in 2006. We modeled biweekly survival as a function of sex, age, movement rate, native versus translocated status, and linear time trend, and then we added year and 3 weather covariates (mean biweekly precipitation and maximum and minimum temperatures). Year and climate variables improved the a priori top model which included movement rate and native versus translocated status. Higher mortality rates due to predation coincided with movements to breeding habitat in late winter, periods of higher temperatures in the spring and summer, and periods of higher precipitation and colder temperatures during the fall–winter seasons. High movement rates of native birds in winter to avoid snow and by translocated birds when dispersing may have led to greater exposure to predators and consequently lower survival rates. Mountain quail can experience low and variable survival, stressing the potential need for multiple years of releases in restoration efforts in the eastern portion of their range. More attention is needed to identify optimal habitat (including nest sites) for restoring mountain quail populations to reduce movements, lower mortality risks, and provide conditions for withstanding periods of unfavorable weather. © 2011 The Wildlife Society.