and
are two novel members of the
family. These phages were isolated on cultures of the plant pathogen
, known for its worldwide economic impact on potato crops. Transmission electron microscopy ...showed viral particles with double-layered icosahedral capsids, and frequent instances of protruding nanotubes harboring a collar-like structure. Mass-spectrometry confirmed the presence of lipids in the virion, and serial purification of colonies from turbid plaques and immunity testing revealed that both phages are temperate.
and
have linear dsDNA chromosomes (18,266 bp and 18,251 bp long, respectively) with the characteristic two-segment architecture of the
. Both genomes encode homologs of the canonical tectiviral proteins (major capsid protein, packaging ATPase and DNA polymerase), as well as PRD1-type virion-associated transglycosylase and membrane DNA delivery proteins. Comparative genomics and phylogenetic analyses firmly establish that these two phages, together with
, form a new genus within the
, which we have tentatively named
. The identification of a cohesive clade of Actinobacteria-infecting tectiviruses with conserved genome structure but with scant sequence similarity to members of other tectiviral genera confirms that the
are an ancient lineage infecting a broad range of bacterial hosts.
Carbohydrate degradation by microbes plays an important role in global nutrient cycling, human nutrition, and biotechnological applications. Studies that focus on the degradation of complex ...recalcitrant polysaccharides are challenging because of the insolubility of these substrates as found in their natural contexts. Specifically, current methods to examine carbohydrate-based biomass degradation using bacterial strains or purified enzymes are not compatible with high-throughput screening using complex insoluble materials. In this report, we developed a small 3D printed filter device that fits inside a microplate well that allows for the free movement of bacterial cells, media, and enzymes while containing insoluble biomass. These devices do not interfere with standard microplate readers and can be used for both short- (24–48 h) and long-duration (> 100 h) experiments using complex insoluble substrates. These devices were used to quantitatively screen in a high-throughput manner environmental isolates for their ability to grow using lignocellulose or rice grains as a sole nutrient source. Additionally, we determined that the microplate-based containment devices are compatible with existing enzymatic assays to measure activity against insoluble biomass. Overall, these microplate containment devices provide a platform to study the degradation of complex insoluble materials in a high-throughput manner and have the potential to help uncover ecologically important aspects of bacterial metabolism as well as to accelerate biotechnological innovation.
Pilitropic and flagellotropic phages adsorb to bacterial pili and flagella. These phages have long been used to investigate multiple aspects of bacterial physiology, such as the cell cycle control in ...the Caulobacterales. Targeting cellular appendages for adsorption effectively constrains the population of infectable hosts, suggesting that phages may have developed strategies to maximize their infective yield. Brevundimonas phage vB_BsubS-Delta is a recently characterized pilitropic phage infecting the Alphaproteobacterium
. Like other Caulobacterales,
divides asymmetrically and its cell cycle is governed by multiple transcriptional regulators, including the master regulator CtrA. Genomic characterization of phage vB_BsubS-Delta identified the presence of a large intergenic region with an unusually high density of putative CtrA-binding sites. A systematic analysis of the positional distribution of predicted CtrA-binding sites in complete phage genomes reveals that the highly skewed distribution of CtrA-binding sites observed in vB_BsubS-Delta is an unequivocal genomic signature that extends to other pilli- and flagellotropic phages infecting the Alphaproteobacteria. Moreover, putative CtrA-binding sites in these phage genomes localize preferentially to promoter regions and have higher scores than those detected in other phage genomes. Phylogenetic and comparative genomics analyses show that this genomic signature has evolved independently in several phage lineages, suggesting that it provides an adaptive advantage to pili/flagellotropic phages infecting the Alphaproteobacteria. Experimental results demonstrate that CtrA binds to predicted CtrA-binding sites in promoter regions and that it regulates transcription of phage genes in unrelated Alphaproteobacteria-infecting phages. We propose that this focused distribution of CtrA-binding sites reflects a fundamental new aspect of phage infection, which we term lytic deferment. Under this novel paradigm, pili- and flagellotropic phages exploit the CtrA transduction pathway to monitor the host cell cycle state and synchronize lysis with the presence of infectable cells.
The dorsal habenular nuclei of the zebrafish epithalamus have become a valuable model for studying the development of left-right (L-R) asymmetry and its function in the vertebrate brain. The ...bilaterally paired dorsal habenulae exhibit striking differences in size, neuroanatomical organization, and molecular properties. They also display differences in their efferent connections with the interpeduncular nucleus (IPN) and in their afferent input, with a subset of mitral cells distributed on both sides of the olfactory bulb innervating only the right habenula. Previous studies have implicated the dorsal habenulae in modulating fear/anxiety responses in juvenile and adult zebrafish. It has been suggested that the asymmetric olfactory-habenula pathway (OB-Ha), revealed by selective labeling from an lhx2a:YFP transgene, mediates fear behaviors elicited by alarm pheromone. Here we show that expression of the fam84b gene demarcates a unique region of the right habenula that is the site of innervation by lhx2a:YFP-labeled olfactory axons. Upon ablation of the parapineal, which normally promotes left habenular identity; the fam84b domain is present in both dorsal habenulae and lhx2a:YFP-labeled olfactory bulb neurons form synapses on the left and the right side. To explore the relevance of the asymmetric olfactory projection and how it might influence habenular function, we tested activation of this pathway using odorants known to evoke behaviors. We find that alarm substance or other aversive odors, and attractive cues, activate fos expression in subsets of cells in the olfactory bulb but not in the lhx2a:YFP expressing population. Moreover, neither alarm pheromone nor chondroitin sulfate elicited fos activation in the dorsal habenulae. The results indicate that L-R asymmetry of the epithalamus sets the directionality of olfactory innervation, however, the lhx2a:YFP OB-Ha pathway does not appear to mediate fear responses to aversive odorants.
Living organisms and their biological properties, including the capacity for transformation and representation of information, offer exciting and inspiring opportunities for transdisciplinary art and ...design explorations. While an emerging body of work is increasingly investigating the possibilities at the intersection of interactive computing, biology, and art, more work is needed to investigate the potential of these approaches for supporting community and public engagement and participation in art, science, and technology. In this project, we describe a multimedia transdisciplinary bioart installation and hands-on agar art activity that we presented to members of the public in a community biology lab setting. Using short interviews, observations, and questionaries, we investigated attendees' reactions and impressions of the experience and found that the event generated transdisciplinary reflections, invited participants to bring their previous knowledge and experience to bear in engaging with different aspects of the work, and that the audience benefited from contextualization by artists.
The Hawaiian cricket genus
Laupala
(Gryllidae: Trigonidiinae) has undergone rapid and extensive speciation, with divergence in male song and female acoustic preference playing a role in maintaining ...species boundaries. Recent study of interspecific differences in the diel rhythmicity of singing and mating, suggests that temporal variation in behavior may reduce gene flow between species. In addition,
Laupala
perform an elaborate and protracted courtship, providing potential for further temporal variation. However, whether these behavioral differences have a genetic basis or result from environmental variation is unknown. We observed courtship and mating in a common garden study of the sympatric species,
Laupala cerasina
and
Laupala paranigra
. We document interspecific differences in the onset and duration of courtship, spermatophore production rate, and diel mating rhythmicity. Our study demonstrates a genetic contribution to interspecific behavioral differences, and suggests an evolutionary pathway to the origins of novel timing phenotypes.
In many organisms, mating behavior occurs at a particular time of day, which may be important for avoiding mate competition or interspecific mating. Crickets of the Hawaiian genus Laupala exhibit an ...unusually protracted courtship in which males produce a series of nuptial gifts prior to the species-typical time of mating. Mating time is one of several rhythmic behaviors that have diverged among closely related Laupala species, which exhibit an extremely high speciation rate. Mating rhythm may reflect direct selection on male and/or female sexual receptivity or the pleiotropic consequence of selection on other rhythmic behaviors. To examine the role of sexual rhythmicity in Laupala cerasina, we characterized the time boundaries or "circadian gate" of courtship and mating, as well as female phonotactic response to male song. We also examined which sex is responsible for mating rhythmicity by phase-shifting males relative to the female photophase. Our results demonstrate that mating behavior is gated by the end of the light phase. Time limits to female mating receptivity were not observed and thus male rhythm alone appears to be responsible for the timing of mating. Furthermore, when courtship is initiated later in the day, males produce fewer nuptial gifts and increase nuptial gift production rate while delaying mating, suggesting that the number of gifts a female receives is important to male reproductive success.
Males of many insect species engage in ritualized behaviours during courtship that include the donation of a food gift to their partner. Although there is extensive diversity in nuptial gift form, a ...gift provided before mating typically serves to facilitate copulation, thereby increasing a male's mating success. Unlike other insects, the Hawaiian swordtail cricket
Laupala shows protracted courtship that includes the serial donation of nuptial gifts prior to mating. Males transfer multiple spermless ‘micro’ spermatophores over several hours before the transfer of a single sperm containing a ‘macro’ spermatophore. By experimental manipulation of male courtship, we tested several hypotheses pertaining to the adaptive significance of protracted courtship involving nuptial gift donation in this system. We found that extensive courtship interactions improve insemination by causing the female reproductive tract to take in more sperm. This suggests that the enhancement of sperm transfer is due to the serial donation of microspermatophores, which would represent a relatively novel function for nuptial gifts provided before mating and highlights the importance of examining cryptic processes of sexual selection.
Magnitudes and patterns of energy expenditure in animal contests are seldom measured, but can be critical for predicting contest dynamics and understanding the evolution of ritualized fighting ...behaviour. In the sierra dome spider, males compete for sexual access to females and their webs. They show three distinct phases of fighting behaviour, escalating from ritualized noncontact display (phase 1) to cooperative wrestling (phase 2), and finally to unritualized, potentially fatal fighting (phase 3). Using CO
2 respirometry, we estimated energetic costs of male–male combat in terms of mean and maximum metabolic rates and the rate of increase in energy expenditure. We also investigated the energetic consequences of age and body mass, and compared fighting metabolism to metabolism during courtship. All three phases involved mean energy expenditures well above resting metabolic rate (3.5×, 7.4× and 11.5×). Both mean and maximum energy expenditure became substantially greater as fights escalated through successive phases. The rates of increase in energy use during phases 2 and 3 were much higher than in phase 1. In addition, age and body mass affected contest energetics. These results are consistent with a basic prediction of evolutionarily stable strategy contest models, that sequences of agonistic behaviours should be organized into phases of escalating energetic costs. Finally, higher energetic costs of escalated fighting compared to courtship provide a rationale for first-male sperm precedence in this spider species.
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