Eukaryotes first: how could that be?

In the half century since the formulation of the prokaryote : eukaryote dichotomy, many authors have proposed that the former evolved from something resembling the latter, in defiance of common (and possibly common sense) views. In such ‘eukaryotes first’ (EF) scenarios, the last universal common ancestor is imagined to have possessed significantly many of the complex characteristics of contemporary eukaryotes, as relics of an earlier ‘progenotic’ period or RNA world. Bacteria and Archaea thus must have lost these complex features secondarily, through ‘streamlining’. If the canonical three-domain tree in which Archaea and Eukarya are sisters is accepted, EF entails that Bacteria and Archaea are convergently prokaryotic. We ask what this means and how it might be tested.     

Acanthamoeba: could it be an environmental host of Shigella?

Shigellosis is a serious public health problem in Korea, because large outbreaks of Shigella sonnei infections were recorded in many parts of the country during the period 1998-2000. However, the epidemiological features of shigellosis are not well known. In this study, we devised conditions suitable for the growth and replication of Shigella in an amoebic intracellular environment, and investigate whether medium conditions affect the survival and replication of Shigella within Acanthamoeba. We evaluated the uptake rates of invasive and non invasive S. sonnei strains by three Acanthamoeba species, namely, A. castellanii Neff, A. astronyxis Ray & Hayes, and A. healyi OC-3A. When A. castellanii Neff was infected with S. sonnei 99OBS1 or 80DH248, shigellae was maintained for a longer time in cytoplasms than in other Acanthamoeba species. S. sonnei 99OBS1 strain (a virulent strain) was recovered in higher numbers than the non-virulent S. sonnei 80DH248 strain in all experiments. Moreover, S. sonnei was more easily engulfed by Acanthamoeba at 18 degrees C. The shigellae uptake rates of Neff strain, which was cultured in free-media (less nutrition), were higher (>10-fold) than those observed in original amoeba culture media (PYG medium) in all time points. S. sonnei 99OBS1 was localized, with an intact membrane, to the vacuoles of Acanthamoeba. We conclude that free-living amoebae more likely act as environmental hosts for shigellae, and thus, may have contributed to outbreaks of shigellosis in Korea.     

Setting an evolutionary trap: could the hider strategy be maladaptive for white-tailed deer?

An evolutionary trap occurs when an organism makes a formerly adaptive decision that now results in a maladaptive outcome. Such traps can be induced by anthropogenic environmental changes, with nonnative species introductions being a leading cause. The recent establishment of coyotes (Canis latrans) into the southeastern USA has the potential to change white-tailed deer (Odocoileus virginianus) population dynamics through direct predation and behavioral adaptation. We used movement rate and bedsite characteristics of radiocollared neonates to evaluate their antipredator strategies in the context of novel predation risk in a structurally homogeneous, fire-maintained ecosystem. Neonate bedsites had greater plant cover values compared with random sites (t = 30.136; p < 0.001), indicating bedsite selection was consistent with the hider strategy used to avoid predation. We determined selection gradients of coyote predation on neonate movement rate and plant cover and diversity at bedsites during the first 10 days of life. Interestingly, neonates that moved less and bedded in denser cover were more likely to be depredated by coyotes, meaning that greater neonate movement rate and bedsites located in less dense cover were favored by natural selection. These results are counter to expected antipredator strategies in white-tailed deer and exemplify how an adaptive response could be maladaptive in novel contexts.     

Obesity and melanoma: could fat be fueling malignancy?

Over the last decade, it has become increasingly clear that adipose tissue, and particularly adipocytes, contributes to tumor progression. Obesity, an ever‐increasing worldwide phenomenon, exacerbates this effect. The influence of obesity on melanoma remains poorly studied, although recent data do underline an association between the two diseases in both humans and murine models. Herein, we review the impact of obesity on melanoma incidence and progression and discuss the underlying mechanisms known to be involved. Adipose tissue favors the proliferation and aggressiveness of melanoma cells through a direct dialog, mediated by soluble factors and by exosomes, and through remodeling of the tumor microenvironment. This knowledge could, in the future, help to design new personalized therapeutic options for obese melanoma patients.     

Protein folding: could hydrophobic collapse be coupled with hydrogen-bond formation?

A judicious examination of an exhaustive PDB sample of soluble globular proteins of moderate size (N<102) reveals a commensurable relationship between hydrophobic surface burial and number of backbone hydrogen bonds. An analysis of 50,000 conformations along the longest all-atom MD trajectory allows us to infer that not only the hydrophobic collapse is concurrent with the formation of backbone amide-carbonyl hydrogen bonds, they are also dynamically coupled processes. In statistical terms, hydrophobic clustering of the side chains is inevitably conducive to backbone burial and the latter process becomes thermodynamically too costly and kinetically unfeasible without amide-carbonyl hydrogen-bond formation. Furthermore, the desolvation of most hydrogen bonds is exhaustive along the pathway, implying that such bonds guide the collapse process.     

Stem cells for reprogramming: could hUMSCs be a better choice?

Human umbilical cord mesenchymal stem cells (hUMSC) are primitive multipotent cells capable of differentiating into cells of different lineages. They can be an alternative source of pluripotent cells since they are ethically and regulatory approved, are easily obtained and have low immunogenicity compared to embryonic stem cells which are dogged with numerous controversies. hUMSC can be a great source for cell and transplantation therapy.     

Eukaryotic origins of DNA replication: could you please be more specific?

Initiation of eukaryotic DNA replication commences when the origin recognition complex (ORC) binds to DNA, recruiting helicases, polymerases, and necessary cofactors. While the biochemical mechanism and factors involved in replication initiation appear to be highly conserved, the DNA sequences at which these events take place in different organisms are not. Thus, while ORC appears to bind to specific DNA sequences in budding yeast, there is increasing new evidence that metazoan ORC complexes do not rely on sequence to be directed to origins of replication. Here, we review examples of specific and non-specific initiation, and we consider what, if not DNA sequence, accounts for DNA binding of ORC to defined regions in eukaryotic genomes.     

Can primaquine therapy for vivax malaria be improved?

The incidence and range of endemic malaria caused by Plasmodium vivax has expanded during the past 30 years. This parasite forms hypnozoites in the liver, creating a persistent reservoir of infection. Primaquine (PQ), introduced 50 years ago, is the only drug available to eliminate hypnozoites. However, lengthy treatment courses and follow-up periods are not conducive to assessing the effectiveness of this drug in preventing relapses. Resistance to standard therapy could be widespread. Studies are urgently needed to gauge this problem and to determine the safety, tolerability and efficacy of shorter courses and higher doses of PQ.     

Can shooting be an effective management tool for foxes? Preliminary insights from a management programme

Historically, shooting has been a popular method for controlling foxes in Australia, but past research has shown it to be an ineffective method for significantly reducing fox population numbers. These past studies investigated shooting when conducted in isolated, one‐off programmes. In more recent years large, coordinated group fox management programmes has become popular in both agricultural and conservation areas. These landscape scale programmes give more chance of long‐term respite from predation damage by slowing down the immigration rates of foxes into the culled area. Studies have been conducted investigating the effectiveness of large‐scale group fox management programmes that primarily used 1080 baiting as the method of control to protect vulnerable livestock and small animal. This study investigated the potential of a large‐scale group programme that used shooting as the main form of control to reduce the impact of fox predation.     

Primary cilium: an elaborate structure that blocks cell division?

A primary cilium is a microtubule-based membranous protrusion found in almost all cell types. A primary cilium has a “9 + 0” axoneme that distinguishes this ancient organelle from the canonical motile “9 + 2” cilium. A primary cilium is the sensory center of the cell that regulates cell proliferation and embryonic development. The primary ciliary pocket is a specialized endocytic membrane domain in the basal region. The basal body of a primary cilium exists as a form of the centriole during interphase of the cell cycle. Although conventional thinking suggests that the cell cycle regulates centrosomal changes, recent studies suggest the opposite, that is, centrosomal changes regulate the cell cycle. In this regard, centrosomal kinase Aurora kinase A (AurA), Polo-like kinase 1 (Plk1), and NIMA related Kinase (Nek or Nrk) propel cell cycle progression by promoting primary cilia disassembly which indicates a non-mitotic function. However, the persistence of primary cilia during spermatocyte division challenges the dominate idea of the incompatibility of primary cilia and cell division. In this review, we demonstrate the detailed structure of primary cilia and discuss the relationship between primary cilia disassembly and cell cycle progression on the background of various mitotic kinases.     

Diabetes and the heart: could the diabetic myocardium be protected by preconditioning?

Both type 1 and type 2 diabetes (insulin-dependent and non-insulin dependent diabetes, respectively) are associated with increased risk for microvascular and macrovascular complications including retinopathy, neuropathy, nephropathy and atherosclerosis. Type 2 diabetes markedly increases the risk for cardiovascular morbidity and mortality, which has major public health implications. In this review, molecular mechanisms pertaining to diabetes-induced heart pathology are addressed.