Genetic analysis of streptomycin-resistant (Sm(R)) strains of Erwinia amylovora suggests that dissemination of two genotypes is responsible for the current distribution of Sm(R) E. amylovora in Michigan

Streptomycin-resistant (Sm(R)) strains of the fire blight pathogen Erwinia amylovora were first isolated in southwest Michigan in 1991. Since that time, resistant strains have progressed northward to other apple-producing regions in the state. A total of 98.7% of Sm(R) strains isolated between 2003 and 2009 in Michigan harbored the strA-strB genes on transposon Tn5393. strA and strB encode phosphotransferase enzymes that modify streptomycin to a nonbactericidal form. Mutational resistance to streptomycin, caused by a point mutation-mediated target-site alteration of the ribosomal S12 protein, occurred in 1.3% of E. amylovora strains from Michigan. Tn5393 was originally introduced to E. amylovora on the plasmid pEa34; thus, the first Sm(R) strains isolated contained both pEa34 and the ubiquitous nonconjugative plasmid pEA29. More recently, we have observed Sm(R) strains in which Tn5393 is present on pEA29, suggesting that the transposon has moved via transposition from pEa34 to pEA29. Almost all of the strains containing Tn5393 on pEA29 had lost pEa34. Of 210 pEA29::Tn5393 plasmids examined, the transposon was inserted at either nucleotide position 1,515 or 17,527. Both of these positions were in noncoding regions of pEA29. Comparative sequencing of the housekeeping genes groEL and potentially variable sequences on pEA29 was done in an attempt to genetically distinguish Sm(R) strains from streptomycin-sensitive (Sm(S)) strains isolated in Michigan. Only 1 nucleotide difference within the total 2,660 bp sequenced from each strain was observed in 2 of 29 strains; multiple sequence differences were observed between the Michigan strains and E. amylovora control strains isolated in the western United States or from Rubus spp. Alterations in virulence observable using an immature pear fruit assay were detected in three of eight Sm(R) strains examined. Our current genetic data indicate that only two Sm(R) strain genotypes (strains containing pEA29::Tn5393 with Tn5393 inserted at either nucleotide position 1,515 or 17,527 on the plasmid) are responsible for the dissemination of Tn5393-encoded streptomycin resistance in Michigan, and that the Sm(R) and Sm(S) strains in Michigan compose a homogenous group.     

Novel PCR primers for detection of genetically diverse virulent <Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis> biovar 1 strains

Novel PCR primers were developed to amplify a 243-bp fragment of an intergenic region between gene 5 and tms2 on the T-DNA of Agrobacterium tumefaciens biovar 1. These primers exhibit 100% positive correlation with strain virulence, 100% negative correlation with avirulence, and did not generate extraneous bands, thus facilitating robust real-time PCR detection.     

Lymphoid follicular cloacal inflammation associated with a novel herpesvirus in juvenile alligators (Alligator mississippiensis).

Multifocal hyperemic nodules and plaques associated with the cloacal mucosa of juvenile alligators (Alligator mississippiensis) at a public aquarium were investigated. Grossly, pale pink to dark red multifocal, circular lesions of varying degrees of severity were identified on the cloacal and, in males, phallus mucosa. Cloacal mucosa biopsies were obtained from 2 of the alligators. These samples were examined histologically and by polymerase chain reaction (PCR) using consensus primers targeting a conserved region of the herpesvirus polymerase gene. Microscopically, the lesions were characterized as submucosal lymphoid follicles with hyperemia and hemorrhage. No inclusion bodies were observed. Minimal to no anisokaryosis was present, and no etiologic agents were identified. Through PCR, a band consistent in size with herpesvirus was observed. Tissues showing similar clinical, histopathologic, and PCR findings were collected from animals at an alligator farm several months later. Sequencing of the PCR amplicon resulted in a 180-base pair sequence that shared 85% sequence identity with tortoise herpesvirus-1.     

The structure of the upper atmosphere of mars: In situ accelerometer measurements from mars global surveyor

The Mars Global Surveyor (MGS) z-axis accelerometer has obtained over 200 vertical structures of thermospheric density, temperature, and pressure, ranging from 110 to 170 kilometers, compared to only three previous such vertical structures. In November 1997, a regional dust storm in the Southern Hemisphere triggered an unexpectedly large thermospheric response at mid-northern latitudes, increasing the altitude of thermospheric pressure surfaces there by as much as 8 kilometers and indicating a strong global thermospheric response to a regional dust storm. Throughout the MGS mission, thermospheric density bulges have been detected on opposite sides of the planet near 90 degreesE and 90 degreesW, in the vicinity of maximum terrain heights. This wave 2 pattern may be caused by topographically-forced planetary waves propagating up from the lower atmosphere.     

Comparison of acid-detergent lignin,alkaline-peroxide lignin,and acid-detergent insoluble ash as internal markers for predicting fecal output and digestibility by cattle offered bermudagrass hays of varying nutrient composition

Camelina sativa is an oil seed crop which can be grown on marginal lands. Camelina seed oil is rich in omega-3 fatty acids (>35%) and γ-tocopherol but is also high in erucic acid and glucosinolates. Camelina meal, is the by-product after the oil has been extracted. Camelina meal was fed to 28 d old weaned pigs at 3.7% and 7.4% until age 56 d. The camelina meal supplements in the soy based diets, improved feed efficiency but also significantly increased the liver weights. Gene expression analyses of the livers, using intra-species microarrays, identified increased expression of phase 1 and phase 2 drug metabolism enzymes. The porcine versions of the enzymes were confirmed by real time PCR. Cytochrome 8b1 (CYP8B1), aldehyde dehydrogenase 2 (Aldh2), and thiosulfate transferase (TST) were all significantly stimulated. Collectively, these genes implicate the camelina glucosinolate metabolite, methyl-sulfinyldecyl isothiocyanate, as the main xeniobiotic, causing increased hepatic metabolism and increased liver weight.     

Comparative renal anatomy of exotic species.

All living organisms consume nutrients that are required for the production of both tissue and energy. The waste products of this process include nitrogenous materials and inorganic salts. They are removed from the body by excretory organs, which in vertebrate shave developed into kidneys and into salt glands in some birds and reptiles. Many invertebrates use a series of excretory organs called nephridia to perform the same function. Even though they perform similar functions, there is no evolutionary connection between invertebrate nephridia and vertebrate kidneys. Both evolved independently.     

Influence of Livestock Grazing Strategies on Riparian Response to Wildfire in Northern Nevada

In 1999–2001 wildfires burned 1.13 million ha across northern Nevada, burning through many grazed riparian areas. With increases in wildfire frequency and extent predicted throughout the Great Basin, an understanding of the interactive effects of wildfire, livestock grazing, and natural hydrologic characteristics is critical. A comparison of pre- and postfire stream surveys provided a unique opportunity to statistically assess changes in stream survey attributes at 43 burned and 38 unburned streams. Livestock grazing variables derived from an extensive federal grazing allotment inventory were used to identify interactive effects of grazing strategies, fire, and natural stressors across 81 independent riparian areas. Differences between baseline and “postfire” stream survey attributes were evaluated for significance using the nonparametric Mann–Whitney test for paired data. Binary logistic regression models evaluated the influence of fire, grazing, and hydrologic characteristics on observed stream survey attribute changes. Grazing attributes contributed most significantly to the bankfull width increase and bank stability rating decrease models. The odds of bankfull width degradation (increase in bankfull width) decreased where there had been rest is some recent years compared to continuous grazing. As the number of days grazed during the growing season increased, the odds of bank stability degradation also increased. The occurrence of fire was not significant in any model. Variation in the riparian width model was attributed primarily to hydrologic characteristics, not grazing. For the models in which grazing variables played a role, stream survey attributes were more likely to improve over time when coupled with a history of rotational grazing and limited duration of use during the growing season. This supports long-term riparian functional recovery through application of riparian complementary grazing strategies.     

Effects of three cold weather event simulations on early life stages of Southern Flounder (Paralichthys lethostigma)

ABSTRACT

To determine the minimum age/size at which Southern Flounder, Paralichthys lethostigma, can safely be moved to outdoor rearing facilities in Texas, we examined survival of simulated temperature drops in two distinct life stages: premetamorphic larvae and two size classes of postmetamorphic juveniles (small = 9.8 ± 0.3 mm in TL; large = 19.7 ± 0.6 mm). Temperature was lowered by ?0.33°C/h to 4°C, 7°C, or 10°C, held for 48 h and then raised at +0.33°C/h back to normal rearing temperature. Fish were monitored daily for survival. Larger postmetamorphic flounder had high survival for all temperature treatments (89%–100% survival), whereas both premetamorphic larvae and smaller postmetamorphic juveniles had low survival (<30%) for all temperature treatments.