Strain persistence of invasive Candida albicans in chronic hyperplastic candidosis that underwent malignant change

Objectives: The aim of this study was to assess persistence and tissue invasion of Candida albicans strains isolated from a 65 year‐old patient with chronic hyperplastic candidosis (CHC), that subsequently developed into squamous cell carcinoma (SCC). Materials and Methods: C. albicans (n=7) were recovered from the oral cavity of the patient over seven years. Confirmation of CHC and SCC in this patient was achieved by histopathological examination of incisional biopsy tissue. DNA fingerprinting was performed on the seven isolates from the CHC patient together with a further eight isolates from patients with normal oral mucosa (n=2), chronic atrophic candidosis (n=1), SCC (n=1) and CHC (n=4). Genotyping involved the use of inter‐repeat PCR using the eukaryotic repeat primer 1251. Characterisation of the tissue invasive abilities of the isolates was achieved by infecting a commercially available reconstituted human oral epithelium (RHE; SkinEthic, Nice, France). After 24 h. C. albicans tissue invasion was assessed by histopathological examination. Results: DNA fingerprinting demonstrated strain persistence of C. albicans in the CHC patient over a seven year period despite provision of systemic antifungal therapy. The strain of C. albicans isolated from this patient was categorised as a high invader within the RHE compared to other isolates. Conclusions: Candidal strain persistence was evident in a patient with CHC over seven years. This persistence may be due to incomplete eradication from the oral cavity following antifungal therapy or subsequent recolonisation from other body sites or separate exogenous sources. The demonstration of enhanced in vitro tissue invasion by this particular strain may, in part, explain the progression to carcinoma.     

A complexity drain on cells in the evolution of multicellularity

A hypothesis has been advanced recently predicting that, in evolution, as higher-level entities arise from associations of lower-level organisms, and as these entities acquire the ability to feed, reproduce, defend themselves, and so on, the lower-level organisms will tend to lose much of their internal complexity (McShea 2001a). In other words, in hierarchical transitions, there is a drain on numbers of part types at the lower level. One possible rationale is that the transfer of functional demands to the higher level renders many part types at the lower level useless, and thus their loss in evolution is favored by selection for economy. Here, a test is conducted at the cell level, comparing numbers of part types in free-living eukaryotic cells (protists) and the cells of metazoans and land plants. Differences are significant and consistent with the hypothesis, suggesting that tests at other hierarchical levels may be worthwhile.     

Born‐digital biodiversity data: Millions and billions

Given the dramatic pace of change of our planet, we need rapid collection of environmental data to document how species are coping and to evaluate the impact of our conservation interventions. To address this need, new classes of “born digital” biodiversity records are now being collected and curated many orders of magnitude faster than traditional data. In addition to the millions of citizen science observations of species that have been accumulating over the last decade, the last few years have seen a surge of sensor data, with eMammal's camera trap archive passing 1 million photo‐vouchered specimens and Movebank's animal tracking database recently passing 1.5 billion animal locations. Data from digital sensors have other advantages over visual citizen science observation in that the level of survey effort is intrinsically documented and they can preserve digital vouchers that can be used to verify species identity. These novel digital specimens are leading spatial ecology into the era of Big Data and will require a big tent of collaborating organizations to make these databases sustainable and durable. We urge institutions to recognize the future of born‐digital records and invest in proper curation and standards so we can make the most of these records to inform management, inspire conservation action and tell natural history stories about life on the planet.     

Reconstructing the evolutionary history of nitrogenases: Evidence for ancestral molybdenum‐cofactor utilization

The nitrogenase metalloenzyme family, essential for supplying fixed nitrogen to the biosphere, is one of life's key biogeochemical innovations. The three forms of nitrogenase differ in their metal dependence, each binding either a FeMo‐, FeV‐, or FeFe‐cofactor where the reduction of dinitrogen takes place. The history of nitrogenase metal dependence has been of particular interest due to the possible implication that ancient marine metal availabilities have significantly constrained nitrogenase evolution over geologic time. Here, we reconstructed the evolutionary history of nitrogenases, and combined phylogenetic reconstruction, ancestral sequence inference, and structural homology modeling to evaluate the potential metal dependence of ancient nitrogenases. We find that active‐site sequence features can reliably distinguish extant Mo‐nitrogenases from V‐ and Fe‐nitrogenases and that inferred ancestral sequences at the deepest nodes of the phylogeny suggest these ancient proteins most resemble modern Mo‐nitrogenases. Taxa representing early‐branching nitrogenase lineages lack one or more biosynthetic nifE and nifN genes that both contribute to the assembly of the FeMo‐cofactor in studied organisms, suggesting that early Mo‐nitrogenases may have utilized an alternate and/or simplified pathway for cofactor biosynthesis. Our results underscore the profound impacts that protein‐level innovations likely had on shaping global biogeochemical cycles throughout the Precambrian, in contrast to organism‐level innovations that characterize the Phanerozoic Eon.     

Three Trends in the History of Life: An Evolutionary Syndrome

The history of life seems to be characterized by three large-scale trends in complexity: (1) the rise in complexity in the sense of hierarchy, in other words, an increase in the number of levels of organization within organisms; (2) the increase in complexity in the sense of differentiation, that is, a rise in the number of different part types at the level just below the whole; and (3) a downward trend, the loss of differentiation at the lowest levels in organisms, a kind of complexity drain within the parts. Here, I describe the three trends, outlining the evidence for each and arguing that they are connected with each other, that together they constitute an evolutionary syndrome, one that has recurred a number times over the history of life. Finally, in the last section, I offer an argument connecting the third trend to the reduction at lower levels of organization in “autonomy”, or from a different perspective, to an increase in what might be called the “machinification” of the lower levels.     

A quantitative formulation of biology's first law

The zero‐force evolutionary law (ZFEL) states that in evolutionary systems, in the absence of forces or constraints, diversity and complexity tend to increase. The reason is that diversity and complexity are both variance measures, and variances tend to increase spontaneously as random events accumulate. Here, we use random‐walk models to quantify the ZFEL expectation, producing equations that give the probabilities of diversity or complexity increasing as a function of time, and that give the expected magnitude of the increase. We produce two sets of equations, one for the case in which variation occurs in discrete steps, the other for the case in which variation is continuous. The equations provide a way to decompose actual trajectories of diversity or complexity into two components, the portion due to the ZFEL and a remainder due to selection and constraint. Application of the equations is demonstrated using real and hypothetical data.     

Seasonal migration by a large forest ungulate: a study on takin (Budorcas taxicolor) in Sichuan Province, China

Migration in large mammals is a biological phenomenon that involves seasonal movements over a vertical or horizontal scale that encompasses distances of more than several home ranges. Takin are large bovid herbivores that conduct seasonal migrations. From 2006 to 2009, we utilized data from 9 GPS-collared animals and 22 trail event recorders to describe takin migration pattern at the level of both individuals and population. We found seasonal migration of takin over an elevation gradient which contained two migration cycles, with takin inhabiting the highest elevations in summer, lowest elevations in spring and autumn, and intermediate elevations during winter. These movements did not involve expansion of home range size but rather shifts in distribution. Habitat availability analysis based on five forest types indicated that takin showed significant monthly forest preferences. Based on both telemetry and trail monitors, mature forest with bamboo understory was the habitat favored by takin for more than 8 months of the year. Both methods also indicated that not all individuals migrated to the highest elevations during summer or the lowest elevations in winter. We also found that individual takin do not necessarily follow the same annual movement, as three out of the four animals with at least 2 years of data changed their migration pattern between years. Current protocols for annual surveys conducted at high-elevation meadows or low-elevation valleys are not adequate to detect all individuals. We suggest that surveys must include all potential habitats and include detection functions in order to accurately estimate takin numbers or relative changes in their density.     

四川唐家河自然保护区扭角羚冬春季日活动模式研究

根据相机陷阱调查获得照片的时间,研究了2008年12月～2009年5月唐家河自然保护区内野生扭角羚Budorcastaxicolor的日活动模式。通过对24个1km×1km样方的调查,共完成686个相机工作日的取样量,获得有效的扭角羚捕捉次数709次(冬季322次,春季387次),并分别计算出扭角羚冬季和春季在各时间段的相对活动强度指数RAI。结果显示,扭角羚在冬季和春季的日活动模式没有显著差异(χ2检验,P>0.1),每天都有3个活跃时期(凌晨、早上和下午)和3个紧随的不活跃时期。其中,冬季日活动的最高峰出现在下午17:00～18:00(RAI=12.42),最低谷出现在日出前3:00～6:00(RAI=0.00);春季最高峰出现在早上6:00～7:00(RAI=20.16),最低谷出现在日出前2:00～5:00(RAI=0.26)。在春季,扭角羚在上午活跃期的活动强度明显高于下午活跃期,而在冬季则相反。春季与冬季相比,扭角羚上午和下午的两个活跃时间段都有提前,可能是由于不同季节气温和光照差异的影响。研究表明,相机陷阱调查技术是研究野生动物在野外活动模式和活动节律的有效工具,可为今后深入开展扭角羚行为生态学...