Document Type


Date of Award


Degree Name

Doctor of Philosophy in Biology - (Ph.D.)


Federated Department of Biological Sciences

First Advisor

Daniel E. Bunker

Second Advisor

Jessica Lee Ware

Third Advisor

Simon J. Garnier

Fourth Advisor

Gareth J. Russell

Fifth Advisor

Gareth J. Russell


Pests of human habitats may harbor and disperse pathogens that cause human disease. One such pest is the German cockroach (Blattella germanica), which is known to harbor numerous pathogens, including Klebsiella and Pseudomonas. The aim of this study is to reveal the importance of the German cockroach as a potential vector of human medically important diseases. To do so, this study investigates German cockroach population structure and their associated bacterial microbiome in urban residential environments. Ninety German cockroaches are collected from three residential apartment buildings in three New Jersey cities. Samples are caught by glue traps and stored at -20°C. DNA and RNA are extracted from cockroach samples and sent for Next Generation Sequencing. Single-Nucleotide Polymorphisms (SNPs) are the genetic markers used for the cockroach population structure analysis. Thirty samples of the same extractions are also used for bacterial genetic analysis. Phylogeny, Principal Component Analysis (PCA), and STRUCTURE analysis are used for characterizing the population structure of cockroaches, which reflects the dispersal ability and colonization history of the cockroach populations. Results show that population structure exists among the three buildings/cities and within each building, and indicates limited gene flow among buildings/cities. Within buildings, genetic population structure indicates both dispersal within buildings and multiple colonization events within each building. 16S rRNA is studied for understanding the bacterial microbiome community on cockroaches, and is used to quantify the abundance of bacterial operational taxonomic units (OTUs) found on the cockroaches. Bacterial microbiome diversity and ordination of OTUs are used to characterize the bacterial microbiome among the 30 samples from the same three buildings/cities. The results show a low but significant differentiation of bacterial community among three buildings and within one building. To test whether the genetic distance of German cockroaches within and among the three buildings is correlated with community distance among bacterial communities on the cockroaches, a Mantel test is implemented. The result of this test is negative, which indicates the lack of correlation between cockroach populations and bacterial communities. A laboratory test of the bacterial dispersal ability of German cockroaches is done by infecting cockroaches with fluorescence-marked E. coli. This test shows the strong bacterial dispersal ability of cockroaches. In conclusion, German cockroach structure is shaped by geographic separation, which doesn’t affect the bacterial community found on the same cockroach populations. These results have several important implications for control of cockroach infestations and for control of the spread of human disease. First, cockroaches are able to spread among within buildings and cockroaches also may colonize a building multiple time. This indicates that control efforts should aim to eliminate cockroaches from all apartments within a building to prevent recolonization from within. Residents should be informed of effective methods to prevent reintroduction from external sources. Second, cockroaches harbor several medically important human bacterial pathogens. Care should be taken not to interact with cockroaches to limit human infection. Third, because bacterial communities do not appear to be strongly shaped by cockroaches, researchers should investigate other mechanisms of bacterial dispersal.



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