The fitness advantage of a high-performance weapon

Weapons used in combat between males are usually attributed to sexual selection, which operates via a fitness advantage for males with weapons of better 'quality'. Because the performance capacity of morphological traits is typically considered the direct target of selection, Darwin's intrasexual selection hypothesis can be modified to predict that variation in reproductive success should be explained by variation in performance traits relevant to combat. Despite such a straightforward prediction, tests of this hypothesis are conspicuously lacking. We show that territorial male collared lizards with greater bite-force capacity sire more offspring than weaker biting rivals but exhibit no survival advantage. We did not detect stabilizing or disruptive selection on bite-force capacity. Taken together, these results support the hypothesis that superior weapon performance provides a fitness advantage through increased success in male contests. Sexual selection on weapon performance therefore appears to be a force driving the evolution and maintenance of sexual dimorphism in head shape.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 840–845.     

微生物对低品位铝土矿生物浸矿的应用潜力

目前,对中低品位铝土矿的利用主要依赖于对传统炼铝工艺及传统选矿工艺的改进。该文在综述微生物在中低品位铝土矿中的运用研究进展,主要集中在微生物对中低品位铝土矿的生物脱硅及生物浸铝,并分析了其作用机制,揭示了利用微生物(细菌和真菌)对铝土矿进行生物脱硅或生物浸铝具有理论和实际可行性,并可对传统炼铝工业形成有效补充。在此基础上,探讨微生物在中低品位铝土矿脱硅及浸铝运用中面临的困难,并逐一展开讨论相应的解决方案,对微生物在中低品位铝土矿中的运用提供参考。     

Clostridium scindens: a human gut microbe with a high potential to convert glucocorticoids into androgens

Clostridium scindens American Type Culture Collection 35704 is capable of converting primary bile acids to toxic secondary bile acids, as well as converting glucocorticoids to androgens by side-chain cleavage. The molecular structure of the side-chain cleavage product of cortisol produced by C. scindens was determined to be 11β-hydroxyandrost-4-ene-3,17-dione (11β-OHA) by high-resolution mass spectrometry, ¹H and ¹³C NMR spectroscopy, and X-ray crystallography. Using RNA-Seq technology, we identified a cortisol-inducible (∼1,000-fold) operon (desABCD) encoding at least one enzyme involved in anaerobic side-chain cleavage. The desC gene was cloned, overexpressed, purified, and found to encode a 20α-hydroxysteroid dehydrogenase (HSDH). This operon also encodes a putative “transketolase” (desAB) hypothesized to have steroid-17,20-desmolase/oxidase activity, and a possible corticosteroid transporter (desD). RNA-Seq data suggests that the two-carbon side chain of glucocorticords may feed into the pentose-phosphate pathway and are used as a carbon source. The 20α-HSDH is hypothesized to function as a metabolic “rheostat” controlling rates of side-chain cleavage. Phylogenetic analysis suggests this operon is rare in nature and the desC gene evolved from a gene encoding threonine dehydrogenase. The physiological effect of 11β-OHAD on the host or other gut microbes is currently unknown.     

Mass spectrometry applications in microbiology beyond microbe identification: progress and potential

Introduction: Mass spectrometry (MS), particularly MALDI-time of flight (MALDI-TOF), has become a routine tool for microorganism identification in clinical microbiology laboratories in the last five years. The use of MALDI-TOF MS has accelerated laboratory analysis, thus providing accurate species-level information with very short turnaround times.

Areas covered: Beyond microbe identification, MALDI-TOF MS offers great opportunities for fast strain typing and detection of antimicrobial susceptibility/resistance in both bacterial and fungal organisms. Drawing on evidence from PubMed literature searches, clinical microbiology laboratory experience, and the authors’ opinions, this review summarizes recent significant advances and ongoing challenges in these areas.

Expert commentary: In the near future, it is expected that the implementation of new analytical algorithms, automation of procedures, and refinement of assays will enhance the clinical and epidemiological usefulness of MALDI-TOF and other MS technologies.     

生物表面活性剂产生菌的筛选

从１０００份土壤和水等样品中,经富集培养、血平板分离、摇瓶培养和排油活性测定等方法筛选出１０株能产生各种生物表面活性剂的菌株（包括细菌,酵母和霉菌）。其中一株细菌产海藻糖脂,一株细菌产鼠李糖脂,两株细菌分别产长碳链不饱和脂肪酸和壬二酸,两株酵母产生的脂多糖具有良好的乳化性能     

The niche of an invasive marine microbe in a subtropical freshwater impoundment

Growing attention in aquatic ecology is focusing on biogeographic patterns in microorganisms and whether these potential patterns can be explained within the framework of general ecology. The long-standing microbiologist''s credo ‘Everything is everywhere, but, the environment selects'' suggests that dispersal is not limiting for microbes, but that the environment is the primary determining factor in microbial community composition. Advances in molecular techniques have provided new evidence that biogeographic patterns exist in microbes and that dispersal limitation may actually have an important role, yet more recent study using extremely deep sequencing predicts that indeed everything is everywhere. Using a long-term field study of the ‘invasive'' marine haptophyte Prymnesium parvum, we characterize the environmental niche of P. parvum in a subtropical impoundment in the southern United States. Our analysis contributes to a growing body of evidence that indicates a primary role for environmental conditions, but not dispersal, in the lake-wide abundances and seasonal bloom patterns in this globally important microbe.     

Myc: a weapon of mass destruction

Growth and proliferation potentiated by deregulated myc oncogene expression is balanced by myc-induced apoptosis. Abrogation of this apoptotic pathway in Myc overexpressing cells leads to cancer progression. Recent work has shown that cell clones in the Drosophila wing disc with higher dMyc expression levels act as supercompetitors to potentiate the programmed death of surrounding normal cells. Yet another paper identifies dE2F1 as a critical component of pathways that normally restrict the ability of growth perturbing genes like dMyc to cause organ overgrowth.     

The Gram-positive side of plant–microbe interactions

Plant growth and development are significantly influenced by the presence and activity of microorganisms. To date, the best-studied plant-interacting microbes are Gram-negative bacteria, but many representatives of both the high and low G+C Gram-positives have excellent biocontrol, plant growth-promoting and bioremediation activities. Moreover, actinorhizal symbioses largely contribute to the global biological nitrogen fixation and many Gram-positive bacteria promote other types of symbioses in tripartite interactions. Finally, several prominent and devastating phytopathogens are Gram-positive. We summarize the present knowledge of the beneficial and detrimental interactions of Gram-positive bacteria with plants to underline the importance of this particular group of bacteria.     

The zebrafish as a model for gastrointestinal tract–microbe interactions

The zebrafish (Danio rerio) has become a widely used vertebrate model for bacterial, fungal, viral, and protozoan infections. Due to its genetic tractability, large clutch sizes, ease of manipulation, and optical transparency during early life stages, it is a particularly useful model to address questions about the cellular microbiology of host–microbe interactions. Although its use as a model for systemic infections, as well as infections localised to the hindbrain and swimbladder having been thoroughly reviewed, studies focusing on host–microbe interactions in the zebrafish gastrointestinal tract have been neglected. Here, we summarise recent findings regarding the developmental and immune biology of the gastrointestinal tract, drawing parallels to mammalian systems. We discuss the use of adult and larval zebrafish as models for gastrointestinal infections, and more generally, for studies of host–microbe interactions in the gut.     

Adhesion as a weapon in microbial competition

Microbes attach to surfaces and form dense communities known as biofilms, which are central to how microbes live and influence humans. The key defining feature of biofilms is adhesion, whereby cells attach to one another and to surfaces, via attachment factors and extracellular polymers. While adhesion is known to be important for the initial stages of biofilm formation, its function within biofilm communities has not been studied. Here we utilise an individual-based model of microbial groups to study the evolution of adhesion. While adhering to a surface can enable cells to remain in a biofilm, consideration of within-biofilm competition reveals a potential cost to adhesion: immobility. Highly adhesive cells that are resistant to movement face being buried and starved at the base of the biofilm. However, we find that when growth occurs at the base of a biofilm, adhesion allows cells to capture substratum territory and force less adhesive, competing cells out of the system. This process may be particularly important when cells grow on a host epithelial surface. We test the predictions of our model using the enteric pathogen Vibrio cholerae, which produces an extracellular matrix important for biofilm formation. Flow cell experiments indicate that matrix-secreting cells are highly adhesive and form expanding clusters that remove non-secreting cells from the population, as predicted by our simulations. Our study shows how simple physical properties, such as adhesion, can be critical to understanding evolution and competition within microbial communities.     

The beneficial sexually transmitted microbe hypothesis of avian copulation

Several hypotheses have been proposed to explain why femalebirds either copulate repeatedly with a single mate or copulatewith multiple partners even though only a single copulationmay be sufficient to fertilize an entire clutch. We hypothesizethat females may directly benefit from high frequencies of copulationand multiple copulation partners if they receive a cloacal inoculationof beneficial sexually transmitted microbes (STMs) that caneither protect them against future encounters with pathogensand/or serve as therapy against present infections. Experimentsin domestic animal production, wildlife rehabilitation, andclinical medicine indicate that inoculations of beneficial microbesderived from the indigenous microflora of hosts can lead tonutritional benefits, resistance to colonization by pathogens,the elimination of infection, and improved immune system functioningin recipients. Our hypothesis predicts greater copulatory rateswhen the probability of the transmission of beneficial microbesexceeds that of pathogens and when the positive effects of beneficialmicrobes on host fitness exceed the negative effects of pathogens.Patterns of copulatory behavior in birds suggest the potentialutility of our hypothesis. We discuss our hypothesis in thecontext of observed patterns of copulation in birds and proposesome ways to directly test our hypothesis. Information on the probabilitiesof transmission during copulation of beneficial and pathogenic microbesand their relative potencies in birds are needed to directlytest the predictions of our hypothesis.