Harvester ant colonies differ in collective behavioural plasticity to regulate water loss.

Collective behavioural plasticity allows ant colonies to adjust to changing conditions. The red harvester ant (Pogonomyrmex barbatus), a desert seed-eating species, regulates foraging activity in response to water stress. Foraging ants lose water to evaporation. Reducing foraging activity in dry conditions sacrifices food intake but conserves water. Within a year, some colonies tend to reduce foraging on dry days while others do not. We examined whether these differences among colonies in collective behavioural plasticity persist from year to year. Colonies live 20-30 years with a single queen who produces successive cohorts of workers which live only a year. The humidity level at which all colonies tend to reduce foraging varies from year to year. Longitudinal observations of 95 colonies over 5 years between 2016 and 2021 showed that differences among colonies, in how they regulate foraging activity in response to day-to-day changes in humidity, persist across years. Approximately 40% of colonies consistently reduced foraging activity, year after year, on days with low daily maximum relative humidity; approximately 20% of colonies never did, foraging as much or more on dry days as on humid days. This variation among colonies may allow evolutionary rescue from drought due to climate change.

Cellular conditions that modulate the fungicidal activity of occidiofungin.

AIMS: To identify cellular conditions that significantly alter susceptibility of Saccharomyces cerevisiae, Candida albicans and Candida glabrata to the antimicrobial peptide, occidiofungin. METHODS AND RESULTS: Genetic and pharmacological approaches were used to determine a role for calcium signalling in occidiofungin sensitivity profiles for S. cerevisiae, C. albicans and C. glabrata strains of yeast. Minimum inhibitory concentration (MIC) and drop assays found that extracellular calcium resulted in a fourfold resistance, and this was independent of an intact calmodulin-calcineurin signalling pathway. A similar resistance was found in the presence of magnesium but not other cations. Occidiofungin was found to be ineffective against cells in a quiescent state when measured by MIC, drop assay and short-term time-kill assays. A similar resistance pattern was detected for S. cerevisiae cultures pre-exposed to cycloheximide or placed in depleted media conditions. CONCLUSIONS: Extracellular calcium results in fungal tolerance to occidiofungin bioactivity outside of the calmodulin-calcineurin pathway. In addition, the resistance of quiescent cells suggests that active cellular growth is a requirement for occidiofungin's mechanism of action. SIGNIFICANCE AND IMPACT OF THE STUDY: The identification of cellular conditions that have a role in the activity of occidiofungin provided insight into potential cellular targets of this novel antifungal.

The behavioral ecology of variation in social insects.

Understanding the ecological relevance of variation within and between colonies has been an important and recurring theme in social insect research. Recent research addresses the genomic and physiological factors and fitness effects associated with behavioral variation, within and among colonies, in regulation of activity, cognitive abilities, and aggression. Behavioral variation among colonies has consequences for survival and reproductive success that are the basis for evolutionary change.

Ant Genetics: Reproductive Physiology, Worker Morphology, and Behavior.

Many exciting studies have begun to elucidate the genetics of the morphological and physiological diversity of ants, but as yet few studies have investigated the genetics of ant behavior directly. Ant genomes are marked by extreme rates of gene turnover, especially in gene families related to olfactory communication, such as the synthesis of cuticular hydrocarbons and the perception of environmental semiochemicals. Transcriptomic and epigenetic differences are apparent between reproductive and sterile females, males and females, and workers that differ in body size. Quantitative genetic approaches suggest heritability of task performance, and population genetic studies indicate a genetic association with reproductive status in some species. Gene expression is associated with behavior including foraging, response to queens attempting to join a colony, circadian patterns of task performance, and age-related changes of task. Ant behavioral genetics needs further investigation of the feedback between individual-level physiological changes and socially mediated responses to environmental conditions.

Implementation of an in-patient pediatric mortality reduction intervention, Gondar University Hospital, Ethiopia.

SETTING: Gondar University Hospital (GUH) is a resource-limited tertiary care hospital in northern Ethiopia. OBJECTIVE: To evaluate the aggregate effect of care standardization, institutional guidelines, and simulation-based training on pediatric mortality at a resource-limited hospital. DESIGN: Uncontrolled pre-post study. GUH in-patients aged from 30 days to 14 years were included in the program evaluation (baseline 11 September-18 November 2010; intervention 19 September-9 December 2011). Interns attached to the GUH pediatrics department from 6 September to 9 December 2011 were included in the training evaluation. Institution-specific management guidelines were prepared for choking, respiratory distress, dehydration, sepsis, congestive heart failure, coma, and seizure. Approval for the protocols was obtained from each pediatric faculty member. Interns received a 3.5 h simulation-based training in triage, procedural skills, and protocol usage. Primary outcome was overall deaths (%); secondary outcomes were deaths within 24 h of admission (%) and median pre/post-training emergency management test scores (%). RESULTS: No difference in mortality (OR 0.72, 95%CI 0.40-1.29, P = 0.265) or first 24 h mortality (crude OR 0.97, 95%CI 0.37-2.55) was observed. Trainee examination scores improved from 33% to 74% (P < 0.001). CONCLUSION: Combining care standardization, management protocols, and simulation-based training did not reduce mortality among pediatric in-patients. Focused, simulation-based training improved short-term test scores among interns.

Contexte : Le centre hospitalier universitaire de Gondar (GUH) est un hôpital de troisième niveau ayant des ressources limitées dans le nord de l'Ethiopie.Objectif : Evaluer l'effet cumulé de la standardisation des soins, des directives institutionnelles et de la formation basée sur la simulation sur la mortalité pédiatrique dans un hôpital aux ressources limitées.Schéma : Etude pré/post non contrôlée. Les patients hospitalisés au GUH âgés de 30 jours à 14 ans ont été inclus dans l'évaluation du programme (avant l'intervention, 11 septembre­18 novembre 2010 ; après l'intervention, 19 septembre­9 décembre 2011). Les internes attachés au service de pédiatrie du GUH du 6 septembre au 9 décembre 2011 ont été inclus dans l'évaluation de la formation. Des directives de prise en charge spécifiques de cette institution ont été préparées pour les cas de suffocation, détresse respiratoire, déshydratation, septicémie, défaillance cardiaque, coma et convulsions. L'approbation de ces protocoles a été obtenue de chaque membre de la faculté de pédiatrie. Les internes ont bénéficié d'une formation basée sur la simulation de 3 à 5 h en matière de triage, compétences procédurales et utilisation des protocoles. Le résultat principal était le taux global de mortalité (%). Les résultats secondaires étaient le décès dans les 24 h suivant l'admission (%), et les scores médians des tests de prise en charge des urgences avant/après la formation (%).Résultats : Aucune différence n'a été observée en termes de mortalité globale (OR 0,72 ; IC95% 0,40­1,29 ; P = 0,265) ou de mortalité pendant les premières 24 h (OR brut 0,97 ; IC95% 0,37­2,55). Par contre, les scores d'examens de prise en charge des personnes formées sont passés de 33% à 74% (P < 0,001).Conclusion : La combinaison de standardisation des soins, de protocoles de prise en charge et de formation basée sur la simulation n'a pas réduit la mortalité des enfants hospitalisés. Cependant, la formation ciblée et basée sur la simulation a amélioré les scores obtenus par les internes dans les tests à court terme.

Marco de referencia: El Hospital Universitario de Gondar (GUH) es un centro de atención terciaria de salud en el norte de Etiopía que cuenta con recursos limitados.Objetivo: Evaluar el efecto agregado de la atención normalizada, la aplicación de directrices institucionales y un programa de capacitación mediante simulación, sobre la mortalidad pediátrica en un hospital de recursos limitados.Métodos: Se llevó a cabo un estudio no comparativo antes y después de la intervención. Los pacientes entre 30 días y 14 años de edad hospitalizados en el GUH se incluyeron la evaluación del programa, cuya fase inicial se realizó entre el 19 de septiembre y el 11 de noviembre del 2010 y la intervención tuvo lugar del 19 de septiembre al 9 de diciembre del 2011. Los internos asociados al servicio de pediatría del hospital participaron en la evaluación de la capacitación del 6 de septiembre al 9 de diciembre del 2011. Se elaboraron directrices institucionales sobre el tratamiento de la asfixia, el síndrome de dificultad respiratoria, la deshidratación, la septicemia, la insuficiencia cardíaca congestiva, el coma y las convulsiones. Se obtuvo la aprobación de los protocolos por parte de todos los miembros del departamento de pediatría. Los internos recibieron una capacitación de 3,5 h mediante técnicas de simulación sobre la selección de los pacientes, la competencia en los procedimientos y la aplicación de los protocolos. El principal criterio de evaluación del estudio fue la mortalidad global y los criterios secundarios fueron la mortalidad en las primeras 24 h de hospitalización y la mediana de la calificación del examen antes y después de la capacitación. Los resultados se expresan en porcentajes.Resultados: No se observó ninguna diferencia en la mortalidad global (OR 0,72; IC95% 0,40­1,29; P = 0,265) y la mortalidad durante las primeras 24 h (OR crudo 0,97; IC95% 0,37­2,55). La puntuación del examen de los internos mejoró después de la capacitación de 33% a 74% (P < 0,001).Conclusión: La intervención que consistió en una atención normalizada, la elaboración de protocolos de tratamiento y la capacitación mediante simulación no disminuyó la mortalidad hospitalaria de los pacientes pediátricos. La capacitación mediante técnicas de simulación con objetivos definidos mejoró las evaluaciones a corto plazo de los internos que participaron.

Social networks and the spread of Salmonella in a sleepy lizard population.

Although theoretical models consider social networks as pathways for disease transmission, strong empirical support, particularly for indirectly transmitted parasites, is lacking for many wildlife populations. We found multiple genetic strains of the enteric bacterium Salmonella enterica within a population of Australian sleepy lizards (Tiliqua rugosa), and we found that pairs of lizards that shared bacterial genotypes were more strongly connected in the social network than were pairs of lizards that did not. In contrast, there was no significant association between spatial proximity of lizard pairs and shared bacterial genotypes. These results provide strong correlative evidence that these bacteria are transmitted from host to host around the social network, rather than that adjacent lizards are picking up the same bacterial genotype from some common source.

Fine-scale genetic structure and dispersal distance in the harvester ant Pogonomyrmex barbatus.

Dispersal has important genetic and evolutionary consequences. It is notoriously difficult to study in some ant species, because reproductives fly from parent nests to mating aggregations and then to new nest sites. We used genetic techniques to measure dispersal distance and characterize patterns of genetic variation in a population of the harvester ant Pogonomyrmex barbatus. This population consists of two interdependent yet genetically distinct mitochondrial lineages, each associated with specific alleles at nuclear loci. We found moderate levels of genetic structure for both lineages and a significant pattern of isolation by distance when individual colonies were the operational unit of study. Dispersal distances calculated from the slope of the regression of genetic on geographic distance were 65.3 m for J1 and 85.8 m for J2. These results are consistent with previous observations of many mating aggregations over small geographic areas. In dependent-lineage populations like our study population, females must mate with males of the opposite lineage to produce workers, and with males of the same lineage to produce female reproductives. Because lineage ratios differ from 1:1 throughout the southwestern United States, restricted dispersal between sites with different lineage ratios could have important effects on dependent-lineage population dynamics. Our results suggest that it is unlikely that many individuals disperse from areas dominated by one lineage to areas dominated by another. Short dispersal distances lead to low gene flow, giving local populations evolutionary independence.

A molecular phylogeny of enteric bacteria and implications for a bacterial species concept.

A molecular phylogeny for seven taxa of enteric bacteria (Citrobacter freundii, Enterobacter cloacae, Escherichia coli, Hafnia alvei, Klebsiella oxytoca, Klebsiella pneumoniae, and Serratia plymuthica) was made from multiple isolates per taxa taken from a collection of environmental enteric bacteria. Sequences from five housekeeping genes (gapA, groEL, gyrA, ompA, and pgi) and the 16S rRNA gene were used to infer individual gene trees and were concatenated to infer a composite molecular phylogeny for the species. The isolates from each taxa formed tight species clusters in the individual gene trees, suggesting the existence of 'genotypic' clusters that correspond to traditional species designations. These sequence data and the resulting gene trees and consensus tree provide the first data set with which to assess the utility of the recently proposed core genome hypothesis (CGH). The CGH provides a genetically based approach to applying the biological species concept to bacteria.

Host and geographical factors influence the thermal niche of enteric bacteria isolated from native Australian mammals.

The thermal profiles of 118 bacterial strains, representing six species of the family Enterobacteriaceae, isolated from a variety of native Australian mammals were determined under in vitro conditions. Each of the bacterial species had a unique thermal profile and differed in their minimum or maximum temperature for growth and in their response to changing temperatures. The taxonomic classification of the host from which the bacterial strains were isolated explained a significant amount of the variation in thermal profile among strains of a species. Host effects were detected at all taxonomic levels: order, family, genus, and species. The locality (State or Territory) or climate zone from which the strain was collected explained a significant amount of the variation in the thermal profile of Citrobacter freundii, Enterobacter cloacae and Klebsiella pneumoniae strains. Genetically similar strains, as determined by allozyme profiles, had similar thermal profiles for the bacterial species Hafnia alvei and Escherichia coli. The results of this study indicate that there are potentially many aspects of host biology that may determine the thermal profile of these bacteria.

Degradation of the kinesin Kip1p at anaphase onset is mediated by the anaphase-promoting complex and Cdc20p.

Kip1p of Saccharomyces cerevisiae is a bipolar kinesin in the conserved bimC kinesin subfamily that mediates mitotic spindle-pole separation. Here, we show that Kip1p is regulated immediately after anaphase initiation by its rapid degradation. Degradation required the ubiquitin protein ligase called the anaphase-promoting complex, the anaphase-promoting complex activating protein Cdc20, and a unique 43-aa sequence in Kip1p. Degradation also required import of Kip1p into the nucleus, but occurred independently of spindle association. A mutation that stabilized Kip1p impaired anaphase progression. The timing of degradation suggests that Kip1p functions primarily during spindle assembly and metaphase, and that Kip1p degradation facilitates structural changes in the mitotic spindle as anaphase progresses.

New World monkey efficacy trials for malaria vaccine development: critical path or detour?

Neither GMP malaria antigens nor GMP vaccines have been compared for efficacy in monkeys and humans. It is too risky to base categorical (go/no go) development decisions on results obtained using partially characterized (non-GMP) antigens, adjuvants that are too toxic for human use or unvalidated primate models. Such practices will lead to serious errors (e.g. failure to identify and stop flawed efforts, rejection of effective vaccine strategies) and unjustifiable delays. Successful malaria vaccine development will emphasize definitive field trials in populations at risk of malaria to define and improve vaccine efficacy.

Qualitative and quantitative differences in cuticular hydrocarbons between laboratory and field colonies of Pogonomyrmex barbatus.

Ants held in the laboratory and field ants of the species Pogonomyrmex barbatus have quantitative differences in their cuticular hydrocarbons and a qualitative difference in their methyl-branched hydrocarbons. Laboratory-held workers showed twice the hydrocarbon content as field ants. This difference was mainly due to higher amounts of straight-chain alkanes and methyl-branched alkanes in laboratory ants, whereas the proportion of the alkenes remained the same for both groups. In addition to the absence of some hydrocarbons in the field colonies, one of the methyl-branched hydrocarbons differed in amount and branching pattern between the two groups of ants. Whereas, notable peaks of 2-methylalkanes were identified in ants kept in the laboratory, these compounds could not be identified in ants living in their natural habitat. However, a trace amount of 4-methyltriacontane was found in lieu of the 2-methyltriacontane counterpart in field ants. Possible explanations for both qualitative and quantitative differences are discussed.

Self-association and precursor protein binding of Saccharomyces cerevisiae Tom40p, the core component of the protein translocation channel of the mitochondrial outer membrane.

The precursor protein translocase of the mitochondrial outer membrane (Tom) is a multi-subunit complex containing receptors and a general import channel, of which the core component is Tom40p. Nuclear-encoded mitochondrial precursor proteins are first recognized by surface receptors and then pass through the import channel. The Tom complex has been purified; however, the protein-protein interactions that drive its assembly and maintain its stability have been difficult to study. Here we show that Saccharomyces cerevisiae Tom40p expressed in bacteria and purified to homogeneity associates efficiently with itself. The self-association is very strong and can withstand up to 4 M urea or 1 M salt. The tight self-association does not require the N-terminal segment of Tom40p. Furthermore, purified Tom40p preferentially recognizes the targeting sequence of mitochondrial precursor proteins. Although the binding of the targeting sequence to Tom40p is inhibited by urea concentrations in excess of 1 M, it is moderately resistant to 1 M salt. Simultaneous self-assembly and precursor protein binding suggest that Tom40p contains at least two different domains mediating these processes. The experimental approach described here should be useful for analysing protein-protein interactions involving individual or groups of components of the mitochondrial import machinery.

Novel wax esters and hydrocarbons in the cuticular surface lipids of the red harvester ant, Pogonomyrmex barbatus.

The cuticular surface lipids of the red harvester ant, Pogonomyrmex barbatus, were found to contain minor amounts of novel wax esters, in addition to the major components, hydrocarbons. The wax esters ranged in carbon number from C19 to C31 and consisted of esters of both odd- and even-numbered alcohols and acids. Each wax ester with a given carbon number eluted at several different retention times indicating possible methyl branching in either the fatty acid or alcohol moiety, or in both moieties. Each eluting peak of wax esters consisted of a mixture of wax esters of the same carbon number in which the fatty acid moiety ranged from C8 to C18, and the alcohol moiety ranged from C8 to C17. Some wax esters were largely found on the head indicating they may be of a glandular origin. The hydrocarbons consisted of: n-alkanes, C23 to C33; odd-numbered n-alkenes, C27 to C35; and the major components, methyl-branched alkanes, C26 to over C49. Notable components of the methyl-branched alkanes were 2-methyltriacontane, and the novel trimethylalkanes with a single methylene between the first and second branch points, 13,15,19-trimethylhentriacontane and 13,15,21-trimethyltritriacontane.

J-domain protein, Jac1p, of yeast mitochondria required for iron homeostasis and activity of Fe-S cluster proteins.

J-proteins are molecular chaperones with a characteristic domain predicted to mediate interaction with Hsp70 proteins. We have previously isolated yeast mutants of the mitochondrial Hsp70, Ssq1p, in a genetic screen for mutants with altered iron homeostasis. Here we describe the isolation of mutants of the J-domain protein, Jac1p, using the same screen. Mutant jac1 alleles predicted to encode severely truncated proteins (lacking 70 or 152 amino acids) were associated with phenotypes strikingly similar to the phenotypes of ssq1 mutants. These phenotypes include activation of the high affinity cellular iron uptake system and iron accumulation in mitochondria. In contrast to iron accumulation, Fe-S proteins of mitochondria were specifically deficient. In jac1 mutants, like in ssq1 mutants, processing of the Yfh1p precursor protein from intermediate to mature forms was delayed. In the genetic backgrounds used in this study, jac1 null mutants were found to be viable, permitting analysis of genetic interactions. The Deltajac1 Deltassq1 double mutant was more severely compromised for growth than either single mutant, suggesting a synthetic or additive effect of these mutations. Overexpression of Jac1p partially suppressed ssq1 slow growth and vice versa. Similar mitochondrial localization and similar mutant phenotypes suggest that Ssq1p and Jac1p are functional partners in iron homeostasis.

A trade-off in task allocation between sensitivity to the environment and response time.

Task allocation is the process that adjusts the number of workers in each colony task in response to the environment. There is no central coordination of task allocation; instead workers use local cues from the environment and from other workers to decide which task to perform. We examine two aspects of task allocation: the sensitivity to the environment of task distribution, and the rate of response to environmental changes. We investigate how these two aspects are influenced by: (1) colony size, and (2) behavioral rules used by workers, i.e. how a worker uses cues from the environment and from social interactions with other workers in deciding which task to perform. We show that if workers use social cues in their choice of task, response time decreases with increasing colony size. Sensitivity of task distribution to the environment may decrease or not with colony size, depending on the behavioral rules used by workers. This produces a trade-off in task allocation: short response times can be achieved by increasing colony size, but at the cost of decreased sensitivity to the environment. We show that when a worker's response to social interactions depends on the local environment, sensitivity of task distribution to the environment is not affected by colony size and the trade-off is avoided.

Distinct roles for two N-terminal cleaved domains in mitochondrial import of the yeast frataxin homolog, Yfh1p.

The yeast frataxin homolog (Yfh1p) participates in mitochondrial iron homeostasis. The phenotypic defects of the Delta yfh1 mutant include drastic accumulation of iron in mitochondria and slow growth. The Yfh1p precursor protein contains two N-terminal domains that are sequentially cleaved by the matrix processing peptidase on import into mitochondria, generating the mature protein. We have precisely mapped these two cleavage sites. Mutations blocking the first or the second cleavage of Yfh1p do not interfere with its in vitro import or with its ability to complement phenotypes of the Delta yfh1 mutant strain. Distinct roles have been ascertained for the two cleaved domains of Yfh1p. The first cleaved domain (domain I) is sufficient for in vitro mitochondrial import of a non-mitochondrial passenger protein. However, neither domain I nor other matrix-targeting signals alone can support efficient in vitro import of mature Yfh1p. The second cleaved domain (domain II) is required as a spacer between a targeting signal and mature Yfh1p. Likewise, when Yfh1p constructs lacking domain I or II are expressed in vivo, they fail to attain appreciable steady-state amounts in mitochondria and cannot complement phenotypes of the Delta yfh1 mutant.

Mechanisms of mitochondrial protein import.

Mitochondria import most of their proteins from the cytosol. Precursor forms of most matrix proteins as well as some IM and IMS proteins are synthesized on cytoplasmic ribosomes with N-terminal cleavable signal sequences. Many other mitochondrial proteins including IM carrier proteins contain internal targeting sequences. Three multisubunit translocases, one in the OM and two in the IM, participate in the import process. These translocases co-operate with cytosolic chaperones, chaperone-like soluble proteins in the IMS as well as chaperones in the matrix. Insertion of carrier proteins into the IM only requires a membrane potential. On the other hand, translocation of preproteins across the IM into the matrix requires (i) a membrane potential, (ii) GTP hydrolysis, which occurs at the outer side of the IM, and (iii) ATP-dependent interactions occurring at the matrix side. Following import, the cleavable signal sequence of most preproteins is removed in one step by the MPP. In some cases, removal of the signal sequence is achieved in two steps; first by MPP and second by either mitochondrial intermediate peptidase or by IM peptidases. Imported proteins must be folded properly to perform their functions.

Variations in antibiotic resistance profile in Enterobacteriaceae isolated from wild Australian mammals.

We carried out a retrospective analysis of 946 strains of Enterobacteriaceae isolated from wild Australian mammals between 1993 and 1997. The prevalence of resistance to fixed concentrations of 32 antimicrobial agents was determined, and the respective roles that taxonomic family of the host, state of origin and bacterial species play in defining prevalence and range of resistance were investigated. Our results demonstrated a low but widespread prevalence of antimicrobial resistance in wild isolates. Only amikacin, ciprofloxacin, meropenem and gentamicin inhibited growth in all 946 samples. There was extensive variation in the combination of antibiotics to which isolates were resistant, and multiple antibiotic resistance was common. Geographical location and host group significantly influenced the antibiotic resistance profile of an isolate, whereas bacterial species influenced both the resistance profile of an isolate and the number of antibiotics it was resistant to. The role of these factors in determining observed antibiotic resistance profiles suggests that any study measuring resistance in wild isolates should include the broadest possible range of bacterial species, host species and sampling locations. As such, this study provides an important new baseline for future measurements of antibiotic resistance in the Australian environment.