Rapid development of cleaning behaviour by Torresian crows Corvus orru on non-native banteng Bos javanicus in northern Australia

In this paper we report the observation of a rapidly developed vertebrate symbiosis involving ectoparasite cleaning by a native corvid of northern Australia, the Torresian crow Corvus orru , on a recently introduced bovid ungulate, the banteng Bos javanicus . Facultative symbioses benefiting both participants (mutualisms) between birds and mammals appear to be rare, despite the apparent advantages obtained by the participants (ecto-parasite removal from the host and food provision to the cleaner). On three separate dates we observed a total of four C. orru individuals eliciting facilitation behaviours by a total of ten female banteng to assist in the removal of ectoparasites. Our observations document the first-known incidence of facultative cleaning behaviour by a native bird species on a non-native, wild vertebrate that has developed in approximately 150 years since the banteng's introduction to Australia.     

Cryopreservation of photosynthetic plant cell suspension cultures

Attempts were made to cryopreserve in liquid nitrogen six different photomixotrophic suspension cultured lines of five different species:Amaranthus powellii Wats.,Datura innoxia Mill.,Glycine max (L.) Merr.,Gossypium hirsutum L. andNicotiana tabacum xNicotiana glutinosa L. fusion hybrid. Only theD. innoxia line, DAT, and theG. max line, SB1, could be successfully recovered as viable, growing, dark green cultures. The successful method utilized a preculture treatment of from 2 to 8 days in a medium containing 3% starch and 3% sorbitol for DAT and 3% sucrose and 3% sorbitol for SB1 cells. The cells survived if frozen with 10% dimethylsulfoxide (DMSO) and 9.1% sorbitol or with 10% DMSO and 8% sucrose. Following a programmed slow-cooling, the cells were thawed in a 40° C bath and could be recovered directly when added to fresh liquid medium. Cryostorage of these lines will save labor and prevent further genetic changes from occurring in these unique suspension cultures.     

Acorn mast drives long-term dynamics of rodent and songbird populations

Resource pulses can have cascading effects on the dynamics of multiple trophic levels. Acorn mast is a pulsed resource in oak-dominated forests that has significant direct effects on acorn predators and indirect effects on their predators, prey, and pathogens. We evaluated changes in acorn mast, rodent abundance, raptor abundance, and reproductive success of a ground-nesting songbird over a 24-year period (1980–2004) in the southern Appalachian Mountains in an effort to determine the relationships among the four trophic levels. In particular, we examined the following: acorn mast from red oaks (Quercus rubra) and white oaks (Q. alba), abundance of white-footed mice (Peromyscus leucopus) and deer mice (P. maniculatus), population estimates of seven raptor species from three feeding guilds, and nest failure and number of juveniles of dark-eyed juncos (Junco hyemalis). Finally, we recorded seasonal temperature and precipitation to determine the effects of weather on each trophic level. We found that weather patterns had delayed effects of up to 3 years on these trophic interactions. Variation in acorn mast, the keystone resource in this community, was explained by weather conditions as far back as 2 years before the mast event. Acorn mast, in turn, was a strongly positive predictor of rodent abundance the following year, whereas spring and summer temperature and raptor abundance negatively affected rodent abundance. Dark-eyed junco nests were more likely to fail in years in which there were more rodents and raptors. Nest failure rate was a strong predictor of the number of juvenile juncos caught at the end of the summer. Our results improve our understanding of the complex ecological interactions in oak-dominated forests by illustrating the importance of abiotic and biotic factors at different trophic levels. Ethan D. Clotfelter and Amy B. Pedersen contributed equally to the writing of this paper.     

Bacterial Distribution in the Lungs of Children with Protracted Bacterial Bronchitis

Objectives

Flexible bronchoscopy with bronchoalveolar lavage (FB-BAL) is increasingly used for the microbiological confirmation of protracted bacterial bronchitis (PBB) in children with a chronic wet cough. At our centre, when performing FB-BAL for microbiological diagnosis we sample 6 lobes (including lingula) as this is known to increase the rate of culture positive procedures in children with cystic fibrosis. We investigated if this is also the case in children with PBB.

Methods

We undertook a retrospective case note review of 50 children investigated for suspected PBB between May 2011 and November 2013.

Results

The median (IQR) age at bronchoscopy was 2.9 (1.7–4.4) years and the median (IQR) duration of cough was 11 (8.0–14) months. Positive cultures were obtained from 41/50 (82%) and 16 (39%) of these patients isolated ≥2 organisms. The commonest organisms isolated were Haemophilus influenzae (25 patients), Moraxella catarrhalis (14 patients), Staphylococcus aureus (11 patients) and Streptococcus pneumoniae (8 patients). If only one lobe had been sampled (as per the European Respiratory Society guidance) 17 different organisms would have been missed in 15 patients, 8 of whom would have had no organism cultured at all. The FB-BAL culture results led to an antibiotic other than co-amoxiclav being prescribed in 17/41 (41%) patients.

Conclusions

Bacterial distribution in the lungs of children with PBB is heterogeneous and organisms may therefore be missed if only one lobe is sampled at FB-BAL. Positive FB-BAL results are useful in children with PBB and can influence treatment.     

MECHANICAL PROPERTIES WITHIN THE GROWTH ZONE OF CORN ROOTS INVESTIGATED BY BENDING EXPERIMENTS II. DISTRIBUTIONS OF MODULUS AND COMPLIANCE IN BENDING

A bending technique was used to infer the spatial distributions of rheological properties within the growth zone of the root of corn, Zea mays. “Bending modulus” (ratio of stress to strain, calculated from engineering theory of bending) falls from 20 MPa near the root tip (3 mm from the tip) to 6 MPa at the location 6 mm from the tip and then remains uniform through the basal region of the growth zone. Where growth stops, at 11–12 mm, there is a sharp rise in bending modulus. The profile of bending moduli is not changed by root incubation temperature during the growth period prior to bending, but it is shifted to the left in roots growing more slowly than the average at either of two temperatures (19 and 29 C). The spatial distribution of “compliance” (reciprocal of bending modulus and a measure of tissue extensibility) resembles the distribution of swelling in response to osmotic perturbation. The distribution of compliance does not parallel that of growth rate. Attempts to explain the discrepancy between compliance and growth rate lead us to examine the theoretical basis for the calculations and to suggest that the dependence of compliance on rate of stretching is physiologically important.     

Selective T cell expansion during aging of CD8 memory repertoires to influenza revealed by modeling

The aging of T cell memory is often considered in terms of senescence, a process viewed as decay and loss of memory T cells. How senescence would affect memory is a function of the initial structure of the memory repertoire and whether the clonotypes that make up the repertoire decay at random. We examine this issue using the T cell memory generated to the conserved influenza A epitope M1(58-66), which induces a strong, focused, but polyclonal CD8 T cell response in HLA-A2 individuals. We analyzed the CD8 T cell memory repertoires in eight healthy middle-aged and eight healthy older blood donors representing an average age difference of ～ 27 y. Although the repertoires show broadly similar clonotype distributions, the number of observable clonotypes decreases significantly. This decrease disproportionally affects low-frequency clonotypes. Rank frequency analysis shows the same two-component clonotype distribution described earlier for these repertoires. The first component includes lower frequency clonotypes for which distribution can be described by a power law. The slope of this first component is significantly steeper in the older cohort. Generating a representative repertoire for each healthy cohort allowed agent-based modeling of the aging process. Interestingly, simple senescence of middle-aged repertoires is insufficient to describe the older clonotype distribution. Rather, a selective clonotype expansion must be included to achieve the best fit. We propose that responses to periodic virus exposure may drive such expansion, ensuring that the remaining clonotypes are optimized for continued protection.     

Distribution of Microbial Physiologic Types in an Aquifer Contaminated by Crude Oil

Abstract We conducted a plume-scale study of the microbial ecology in the anaerobic portion of an aquifer contaminated by crude-oil compounds. The data provide insight into the patterns of ecological succession, microbial nutrient demands, and the relative importance of free-living versus attached microbial populations. The most probable number (MPN) method was used to characterize the spatial distribution of six physiologic types: aerobes, denitrifiers, iron-reducers, heterotrophic fermenters, sulfate-reducers, and methanogens. Both free-living and attached numbers were determined over a broad cross-section of the aquifer extending horizontally from the source of the plume at a nonaqueous oil body to 66 m downgradient, and vertically from above the water table to the base of the plume below the water table. Point samples from widely spaced locations were combined with three closely spaced vertical profiles to create a map of physiologic zones for a cross-section of the plume. Although some estimates suggest that less than 1% of the subsurface microbial population can be grown in laboratory cultures, the MPN results presented here provide a comprehensive qualitative picture of the microbial ecology at the plume scale. Areas in the plume that are evolving from iron-reducing to methanogenic conditions are clearly delineated and generally occupy 25–50% of the plume thickness. Lower microbial numbers below the water table compared to the unsaturated zone suggest that nutrient limitations may be important in limiting growth in the saturated zone. Finally, the data indicate that an average of 15% of the total population is suspended. Received: 28 October 1998; Accepted: 26 February 1999