BRC-BIO: Bird feeders in the city: the effect of urbanization on ecological immunology and microbiology in cardueline finches

城市鸟类饲养者促进了以种子为食的鸟类之间的社会接触，增加了与含有抗生素耐药性基因的细菌的潜在接触。这对接触受污染的鸟类喂食器的鸟类和人类产生了负面影响，因为他们可能会从这些喂食器中获得抗药性细菌。表现出强烈免疫反应的鸟类可能不会受到这些微生物的伤害，但城市环境会给鸟类带来压力，从而阻碍它们的免疫系统。此外，城市发展导致栖息地碎片化，这可以减少有益的免疫基因变种在农村和城市鸟类种群之间的传播，这些物种的分布有限。为了探索这些问题，研究人员将沿着城乡梯度收集三个地点的数据，以了解加州经常使用鸟类喂食器的三种雀类物种的数据。该项目的目的是(1)测量鸟类和鸟类喂食者中是否存在抗菌素耐药基因，(2)测量鸟类的体外杀菌能力，以及(3)测量家雀体内六种免疫基因之间的差异。研究人员将通过一个地区观鸟协会和童子军组织让社区参与进来。他们还将让他们为少数族裔服务的机构的四门课程的学生帮助收集、处理和分析他们的数据。最终，他们的目标是增加历史上被边缘化的人在科学研究中的参与，并就人类如何影响鸟类健康以及如何帮助保护当地鸟类种群的重要性与公众建立联系。在加利福尼亚州弗雷斯诺附近的城乡梯度上，研究人员将通过进行杀菌测试和分析白细胞图谱，研究城市化对三种雀类物种(松松、金翅雀和家雀血淋病)先天免疫的影响。研究人员将测量非迁徙家雀主要组织相容性复合体(MHC；适应性免疫系统的基石)和Toll样受体(TLRs；先天免疫基因)以及中性基因的免疫遗传多样性和分化，这些家雀通常在农村和城市环境中觅食。研究人员将量化和描述细菌及其抗菌素耐药基因(ARGs)在这些鸟类和鸟类喂食者中的流行情况。为此，研究人员和他们的学生将捕获并采集城乡梯度上的雀类样本，以(1)通过对三种细菌进行杀菌试验来测量固有免疫力，并用光学显微镜分析白细胞谱；(2)通过高通量测序确定MHC I类和II类病原体识别结构域的遗传特征，测量免疫遗传变异；并使用14个微卫星基因座测量中性遗传多样性；(3)进行元基因组分析，以表征三种雀类及其所用鸟类喂食器中的微生物和ARG。最终，这项研究将使生物学家更好地了解城市化如何在鸟类免疫系统的进化生态和含有ARG的微生物的传播中发挥作用。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Urban bird feeders promote social contact between seed-eating birds, increasing potential exposure to bacteria containing antibiotic resistance genes. This has negative consequences for birds and humans who handle soiled bird feeders, as they may acquire antibiotic-resistant bacteria from these feeders. Birds exhibiting strong immune responses may not be harmed by these microbes, but urban environments can stress birds and thereby impede their immune system. Also, urban development causes habitat fragmentation, which can decrease the spread of beneficial immune gene variants between rural and urban bird populations in species with limited dispersal. To explore these issues, the researchers will gather data across three sites along an urban-rural gradient for three finch species that routinely occupy bird feeders in California. The project aims are to (1) measure the presence of antimicrobial resistance genes in birds and at bird feeders, (2) measure the birds' bacteria-killing ability in vitro, and (3) measure the variation between six immune genes in house finches. The researchers will involve the community through a regional birding society and scouting organizations. They will also have students in four courses at their minority-serving institution help collect, process, and analyze their data. Ultimately, their goal is to increase the participation of historically marginalized people in scientific research and connect with the public on the importance of how humans can impact avian health and how they can help protect local bird populations.Along an urban-rural gradient near Fresno, California, the researchers will study the effect of urbanization on the innate immunity of three finch species (pine siskins Spinus pinus, lesser goldfinches Spinus psaltria, and house finches Haemorhous mexicanus) by performing bacteria-killing assays and analyzing leukocytes profiles. The researchers will measure immunogenetic diversity and differentiation of the major histocompatibility complex (MHC; the cornerstone of the adaptive immune system) and Toll-like receptors (TLRs; innate immune genes) and at neutral loci in non-migratory house finches, which commonly occupy feeders in rural and urban environments. The researchers will quantify and characterize the prevalence of bacteria and their antimicrobial resistance genes (ARGs) in these birds and on the bird feeders. To accomplish this, the researchers and their students will catch and sample finches along an urban-rural gradient to (1) measure constitutive innate immunity by running bacteria-killing assays against three bacteria species and analyze leukocyte profiles with light microscopy; (2) measure immunogenetic variation by genetically characterizing the hypervariable peptide-binding region of MHC class I and II using high-throughput sequencing, the pathogen-recognition domains of four TLRs, and measure neutral genetic diversity using 14 microsatellite loci; and (3) perform metagenomic analysis to characterize microbes and ARGs in the three finches and the bird feeders they use. Ultimately, this research will allow biologists to better understand how urbanization plays a role in the evolutionary ecology of the avian immune system and the spread of microbes containing ARGs.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.