Joseph L. Graves

The effect of superoxide dismutase alleles on aging in Drosophila

The effects of superoxide dismutase on aging were tested using two differt experimental approaches. In the first, replicated populations with postponed aging were compared with their controls for frequencies of electrophoretic alleles at the SOD locus. Populations with postponed aging had consistently greater frequencies of the allele coding for more active SOD protein. This allele was not part of a segregating inversion polymorphism. The second experimental approach was the extraction ofSOD alleles from different natural populations followed by the construction of differentSOD genotypes on hybrid genetic backgrounds. This procedure did not uncover any statistical effect ofSOD genotype on hybrid genetic backgrounds. This effects on longevity and fecundity due to the family from which a particularSOD genotype was derived. To detect the effects ofSOD genotypes on longevity with high probability would require a ten-fold increase in the number of families used.

Rapid evolution of silver nanoparticle resistance in Escherichia coli

The recent exponential increase in the use of engineered nanoparticles (eNPs) means both greater intentional and unintentional exposure of eNPs to microbes. Intentional use includes the use of eNPs as biocides. Unintentional exposure results from the fact that eNPs are included in a variety of commercial products (paints, sunscreens, cosmetics). Many of these eNPs are composed of heavy metals or metal oxides such as silver, gold, zinc, titanium dioxide, and zinc oxide. It is thought that since metallic/metallic oxide NPs impact so many aspects of bacterial physiology that it will difficult for bacteria to evolve resistance to them. This study utilized laboratory experimental evolution to evolve silver nanoparticle (AgNP) resistance in the bacterium Escherichia coli (K-12 MG1655), a bacterium that does not harbor any known silver resistance elements. After 225 generations of exposure to the AgNP environment, the treatment populations demonstrated greater fitness vs. control strains as measured by optical density (OD) and colony forming units (CFU) in the presence of varying concentrations of 10 nm citrate-coated silver nanoparticles (AgNP) or silver nitrate (AgNO3). Genomic analysis shows that changes associated with AgNP resistance were already accumulating within the treatment populations by generation 100, and by generation 200 three mutations had swept to high frequency in the AgNP resistance stocks. This study indicates that despite previous claims to the contrary bacteria can easily evolve resistance to AgNPs, and this occurs by relatively simple genomic changes. These results indicate that care should be taken with regards to the use of eNPs as biocides as well as with regards to unintentional exposure of microbial communities to eNPs in waste products.

Against racial medicine

ABSTRACT Some scholars claim that recent studies of human genetic variation validate the existence of human biological races and falsify the idea that human races are socially constructed misconceptions. They assert that analyses of DNA polymorphisms unambiguously partition individuals into groups that are very similar to lay conceptions of race. Furthermore, they propose that this partitioning allows us to identify specific loci that can explain contemporary health disparities between the supposed human races. From this, it appears that racial medicine has risen again. In this essay Graves and Rose construct a case against racial medicine. Biological races in other species are strongly differentiated genetically. Because human populations do not have such strong genetic differentiation, they are not biological races. Nonetheless, the lack of population genetic knowledge among biomedical researchers has led to spuriously racialized human studies. But human populations are not genetically disjoint. Social dominance may lead to medical differences between socially constructed races. In order to resolve these issues, medicine should take both social environment and population genetics into account, instead of dubious ‘races’ that inappropriately conflate the two.

Genomics of Parallel Experimental Evolution in Drosophila

Abstract What are the genomic foundations of adaptation in sexual populations? We address this question using fitness–character and whole-genome sequence data from 30 Drosophila laboratory populations. These 30 populations are part of a nearly 40-year laboratory radiation featuring 3 selection regimes, each shared by 10 populations for up to 837 generations, with moderately large effective population sizes. Each of 3 sets of the 10 populations that shared a selection regime consists of 5 populations that have long been maintained under that selection regime, paired with 5 populations that had only recently been subjected to that selection regime. We find a high degree of evolutionary parallelism in fitness phenotypes when most-recent selection regimes are shared, as in previous studies from our laboratory. We also find genomic parallelism with respect to the frequencies of single-nucleotide polymorphisms, transposable elements, insertions, and structural variants, which was expected. Entirely unexpected was a high degree of parallelism for linkage disequilibrium. The evolutionary genetic changes among these sexual populations are rapid and genomically extensive. This pattern may be due to segregating functional genetic variation that is abundantly maintained genome-wide by selection, variation that responds immediately to changes of selection regime.

Great Is Their Sin: Biological Determinism in the Age of Genomics

The roots of biological determinism are ancient. Yet despite advances in biological science in the twentieth century, determinist thinking has not been eliminated. This article reviews the history of biological determinism, examining its varieties from its creationist beginnings to present-day biological thinking in the age of genomics. It elucidates the relationship between biological determinism and racialist understandings of human genetic variation. Of particular importance in this regard are the ongoing claims of racial medicine (a modern biological determinist variety) as well as resurgent attempts to classify humans into biological races utilizing genomic data and clustering algorithms (such as STRUCTURE). Finally it presents how the complexity of biological variation generated by genetic, epigenetic, environmental, and chance effects vitiates simplistic biological determinism.

Biological V. Social Definitions of Race: Implications for Modern Biomedical Research

Misconceptions concerning the concordance of biological and social definitions of race are ongoing in American society. This problem extends beyond that of the lay public into the professional arena, especially that of biomedical research. This continues, in part, because of the lack of training of many biomedical practitioners in evolutionary thinking. This essay reviews the biological and social definitions of race, examining how understanding the evolutionary mechanisms of disease is crucial to addressing ongoing health disparities. Finally it concludes by laying bear the fallacies of “race-specific” medicine.

Antimicrobial Nanomaterials: Why Evolution Matters

Due to the widespread occurrence of multidrug resistant microbes there is increasing interest in the use of novel nanostructured materials as antimicrobials. Specifically, metallic nanoparticles such as silver, copper, and gold have been deployed due to the multiple impacts they have on bacterial physiology. From this, many have concluded that such nanomaterials represent steep obstacles against the evolution of resistance. However, we have already shown that this view is fallacious. For this reason, the significance of our initial experiments are beginning to be recognized in the antimicrobial effects of nanomaterials literature. This recognition is not yet fully understood and here we further explain why nanomaterials research requires a more nuanced understanding of core microbial evolution principles.

Mechanobiology of Antimicrobial Resistant Escherichia coli and Listeria innocua

A majority of antibiotic-resistant bacterial infections in the United States are associated with biofilms. Nanoscale biophysical measures are increasingly revealing that adhesive and viscoelastic properties of bacteria play essential roles across multiple stages of biofilm development. Atomic Force Microscopy (AFM) applied to strains with variation in antimicrobial resistance enables new opportunities for investigating the function of adhesive forces (stickiness) in biofilm formation. AFM force spectroscopy analysis of a field strain of Listeria innocua and the strain Escherichia coli K-12 MG1655 revealed differing adhesive forces between antimicrobial resistant and nonresistant strains. Significant increases in stickiness were found at the nanonewton level for strains of Listeria innocua and Escherichia coli in association with benzalkonium chloride and silver nanoparticle resistance respectively. This advancement in the usage of AFM provides for a fast and reliable avenue for analyzing antimicrobial resistant cells and the molecular dynamics of biofilm formation as a protective mechanism.

Factors influencing minority student decisions to consider a career in evolutionary biology

BackgroundWithout an understanding of evolution, members of the public are unlikely to fully grasp many important issues necessary for the understanding science. In addition, evolutionary science plays an important role in advancing many other STEM disciplines. In stark contrast to the importance of the evolutionary sciences, is its enigmatic acceptance by the general American public. This acceptance is also not uniform within African American, Hispanic, and American Indian populations, who show higher rates of rejection of evolutionary reasoning. In an effort to advance our scientific community, it is imperative that we recruit highly quality students from an ever-increasing diverse population. Thus, the field is failing to attract and maintain the diversity desired in America’s scientific workforce with the above-mentioned minority groups, which are even further underrepresented in evolutionary science.MethodsTo examine why underrepresented minorities may not choose careers in evolutionary sciences, we surveyed 184 people who have chosen to pursue a career in science. The two questions we examined were: (1) what factors influence the career choices of underrepresented minorities (URMs) interested in science? and (2) what factors influence these URM students to choose careers in other sub-disciplines in biology rather than careers in evolutionary science? A survey was created from previously published research, and our analysis examined statistical differences between different racial/ethnic groups.ResultsOur data suggest there are significant differences among racial/ethnic groups in factors that appear to influence their career paths, specifically African Americans and non-Puerto Rican Hispanic/Latino(a)s place greater emphasis on the presence of people of similar racial/ethnic background. Additionally we found differences between the URM groups in terms of their interest in, and understanding of, evolutionary biology; which appears to result in less likelihood of choosing careers in evolutionary science. And for some African Americans, reluctance to pursue evolutionary biology may be tied to holding misconceptions about evolution and higher levels of religiosity.ConclusionsOur current work is preliminary, but once there is a better understanding of why URMs do not pursue evolutionary science, strategic steps can be taken to overcome these barriers. When an inclusive culture is at work, a diverse scientific team becomes capable of producing a broad range of original and engaging ideas not possible among homogenous groups. Educators, researchers, and equality advocates will be able to target the specific causes of underrepresentation in the evolutionary sciences and improve representation of racial and ethnic minorities in evolutionary science, to the ultimate benefit of the greater scientific community and the world at large.

Why the Nonexistence of Biological Races Does Not Mean the Nonexistence of Racism

Color-blind racism is an ideology that allows persons of the dominant socially defined race (European Americans) to claim that racism is no longer the central factor determining the life chances of persons of non-European descent (particularly dark-skinned individuals of African descent). They argue that instead of the ongoing institutional and individual racism of American society, nonracial factors such as market dynamics, naturally occurring phenomena, and the cultural attitudes of minorities themselves are the main causal factors of their social subordination. Concurrent with the rise of this ideology has been the scientific determination that the human species does not really contain biological races. Thus, many color-blind racists have co-opted this fact to further argue that racism can no longer exist, since we have no biological races. This article will not only outline the nature of human biological variation, why that variation does not justify the classification of biological races within the species, but also why this fact has absolutely nothing to do with the ongoing racial discrimination faced by persons with dark skins in the United States. Furthermore, it will explain why membership in a socially defined race has real biological consequences including reducing the mental and physical well-being of the socially subordinated.