Cooperation and conflict in quorum-sensing bacterial populations

It has been suggested that bacterial cells communicate by releasing and sensing small diffusible signal molecules in a process commonly known as quorum sensing (QS). It is generally assumed that QS is used to coordinate cooperative behaviours at the population level. However, evolutionary theory predicts that individuals who communicate and cooperate can be exploited. Here we examine the social evolution of QS experimentally in the opportunistic pathogen Pseudomonas aeruginosa, and show that although QS can provide a benefit at the group level, exploitative individuals can avoid the cost of producing the QS signal or of performing the cooperative behaviour that is coordinated by QS, and can therefore spread. We also show that a solution to the problem of exploitation is kin selection, if interacting bacterial cells tend to be close relatives. These results show that the problem of exploitation, which has been the focus of considerable attention in animal communication, also arises in bacteria.     

Zircon U-Pb dating and Lu-Hf isotope study of intermediate-mafic sub-volcanic and intrusive rocks in the Lishui Basin in the middle and lower reaches of Yangtze River

Eight Mesozoic sub-volcanic and intrusive rocks in the Lishui Basin have been selected for zircon U-Pb dating and Lu-Hf isotopic analysis. The Laohutou, Datongshan,Daweizhuang, Yeshanao, Yanwaqiao, Xibeishan, Changshantou and Jianshan porphyrites yield concordant early Cretaceous ages of 130.5 ± 1.6 Ma, 136.0 ± 3.4 Ma, 132.7 ±2.7 Ma, 127.0 ± 1.9 Ma, 129.4 ± 1.7 Ma, 133.2 ± 2.1 Ma,131.1 ± 2.3 Ma and 127.4 ± 1.8 Ma, respectively. Zircon eHf(t) values for these rocks range from-3.54 to-9.11, mostly between-3.54 and-5.93, suggesting sources similar to those for coeval igneous rocks in other volcanic basins along the middle and lower reaches of Yangtze River. Considering the geochemical characteristics of coeval magmatic rocks in the middle and lower reaches of Yangtze River and its adjacent areas, this paper proposes a model of slab rollback to explain the Mesozoic magmatism in the east-central part of China continent. In the middle-late Jurassic to early Cretaceous(170–135 Ma), the Pacific plate started to subduct beneath the Eurasian continent, producing a compressive tectonic setting,and magmatism progressed from coast to the inland. The magmas of this period were derived mostly from partial melting of ancient crust. After *135 Ma, the subduction weakened, and the rollback of the subducted Pacific plate produced an extensional environment. This led to the formation of volcanic basins, the partial melting of enriched mantle sources and less ancient crust, and the intrusion of voluminous intermediate-mafic igneous rocks.     

华夏南部可能存在Grenville期造山作用: 来自基底变质岩中锆石U-Pb定年及Lu-Hf同位素信息

对华夏地块南部粤中增城和赣南鹤仔3个基底变质岩的地球化学和碎屑锆石年代学研究表明, 它们的原岩都是形成于晚新元古代的沉积岩. 3个变质沉积岩都主要由新元古代早期(1.0~0.9 Ga)的碎屑物质组成, 并混有少量中元古代和新元古代中晚期(0.8~0.6 Ga)的碎屑物, 说明沉积物主要来源于一个遭受过Gondwana大陆聚合事件影响的Grenville期造山带. 碎屑锆石的Hf同位素成分显示这些Grenville期锆石可能是造山旋回早期形成的弧与古老大陆碰撞产生的岩浆结晶的. 结合华夏地块其他地区~1.0 Ga年龄锆石的分布及形态学特征, 本文认为华夏地块的南缘很可能曾经存在或者极其靠近一个Grenville期的造山带. 而这期造山作用的时代与东印度以及东南极的Grenville造山带一致, 且同样受到Gondwana大陆聚合事件的影响. 因此, 从Rodinia超大陆裂解到Gondwana超大陆聚合期间, 华南地块很可能位于澳大利亚西部而与东印度和东南极相邻.     

Finding of ancient materials in Cathaysia and implication for the formation of Precambrian crust

U-Pb dating for fifty-six detrltsl zircons from a paragneiss in Nanxiong area, northern Guangdong Province, Indicates that the latest Neoproterozoic sediments in Cathaysia hinterland are composed of numerous Grenvillian and Necerchaean clasUc materials, as well as some Mesoproterozolc detritus. Minor Paleoarchaean （3.76 Ga） and Mesoarchaean （3.0-3.2 Ga） zircons, which are the oldest zircons In South China, also are firstly found in the sediments, suggesting that the Cathaysia Block may contsln very old materials. The Hf isotope compositions of thirty-seven zircons reveal that these clastlc materials have different origins. Minor zircons crystslllzed from magma generated from relatively juvenile crust, while the parental magma of most zircons was derived from ancient crust. Integration of U-Pb dating and Hf Isotope analysis of these zircons suggests that the generation of juvenile crust in the Cathaysia block mainly occurred at 2.5-2.6 Ga. Mesoarchaean （3.0-3.3 Ga）, late Paleoproterozolc （-1.8 Ga） and Paleoarchaean （-3.7 Ga） may also be important episodes of crustal growth. Grenvllllan magmatism is extremely Intense, but it mainly involved recycling of ancient crustal components with little formation of Juvenile crust. The marked presence of -2.1 Ga Hf model ages and the absence of the zircons with crystsllizatlon ages at -2.1 Ga suggest that the parental magma of many zircons was probably derived from the mixed source consisting of Neoarchaean and late Paleoproterozoic materlals.     

Only full-sibling families evolved eusociality

Arising from M. A. Nowak, C. E. Tarnita & E. O. Wilson 466, 1057-1062 (2010); Nowak et al. reply. The paper by Nowak et al. has the evolution of eusociality as its title, but it is mostly about something else. It argues against inclusive fitness theory and offers an alternative modelling approach that is claimed to be more fundamental and general, but which, we believe, has no practical biological meaning for the evolution of eusociality. Nowak et al. overlook the robust empirical observation that eusociality has only arisen in clades where mothers are associated with their full-sibling offspring; that is, in families where the average relatedness of offspring to siblings is as high as to their own offspring, independent of population structure or ploidy. We believe that this omission makes the paper largely irrelevant for understanding the evolution of eusociality.     

Myristic acid is coupled to a structural protein of polyoma virus and SV40

In the lytic cycle of papova viruses, both uncoating of the viral genome after infection and assembly of functional virions take place in the cell nucleus. The mechanisms by which newly internalized virions are targeted to the nucleus and viral DNA encapsidated into particles are poorly understood. Although the major capsid protein VP1 is involved in endocytosis, and largely defines virion structure, the functions of the minor proteins VP2 and VP3 have remained obscure. Here we show that VP2 from both polyoma virus and simian virus 40 (SV40) is covalently linked to myristic acid; this is the first report of a myristylated protein in the nucleus and of a fatty acid being important in the structure of a nonenveloped virus. We consider the implications of this unusual modification on encapsidation and suggest that VP2 may be a scaffolding protein for virion assembly.     

Perspectives on forecasting research in accounting and finance

This paper offers some perspectives on forecasting research in accounting and finance. It is maintained that many common areas of forecasting research exist. Yet, most research has focused upon a particular (Box-Jenkins) technique and a particular (reported earnings) variable, virtually neglecting numerous other relevant forecasting research topics. This symposium issue includes papers which address several of these neglected research topics. The eight papers constituting the issue are classified into three categories: (1) univariate time-series modelling; (2) multivariate time-series modelling; and (3) comparison of experts' forecasts with those of statistical models. Following a summary of the papers, some suggestions for future research are offered.     

Formation history and protolith characteristics of granulite facies metamorphic rock in Central Cathaysia deduced from U-Pb and Lu-Hf isotopic studies of single zircon grains

The petrochemical as well as zircon U-Pb and Lu-Hf isotopic studies of granulite facies metamorphic rock from the Tao＇xi Group in eastern Nanling Range, Central Cathaysia indicate that its protolith is the sedimentary rock with low maturation index. The clastic materials are mostly from middle Neoproterozoic （-736 Ma） granitoid rocks with minor Neoarchaean and Paleoproterozoic rocks. The timing of this Neoproterozoic magmatism is in agreement with the second period of magmatism widespread surrounding the Yangtze Block. Hf isotopic data indicate that the Neoproterozoic granitoids resulted from the recycled Paleoproterozoic mantle-derived crustal materials. The sedimentary rock was deposited in Late Neoproterozoic Era, and carried into low crust in Early Paleozoic. The partial melting of the meta-sedimentary rock took place at about 480 Ma and subsequently granulite facies metamorphism occurred at ca. 443 Ma. The zircons forming during this time interval （Early Paleozoic） show large Hf isotope variations, and their ZHf（t） values increase from -13.2 to ＋2.36 with decreasing age, suggesting the injection of mantle-derived materials during partial melting and metamorphism processes in the Early Paleozoic. Calculation results show that this metamorphic rock, if evolved to Mesozoic, has similar isotopic composition to the nearby Mesozoic high Si peraluminous granites, implying that this kind of granulite facies metamorphic rock is probably the source material of some Mesozoic peraluminous granitoids in eastern Nanling Range.