The kinetochore has been viewed as playing a critical role in many aspects of chromosome dynamics as the cell progresses through mitosis. This includes chromosome congression and alignment on the metaphase plate and sister chromosome separation and segregation to the spindle poles. Defects in kinetochore function result in mitotic errors and aneuploidy. Thus, the finding that chromosome fragments lacking a kinetochore (acentrics) are capable of normal congression, sister separation and segregation is fascinating. My thesis takes advantage of a Drosophila system in which acentrics can be efficiently generated and their behavior analyzed through live fluorescence analysis. In Chapter 1, we review how cells transmit chromosomes through mitosis without canonical kinetochore-microtubule interactions. Decades of research and a collection of studies reveal that microtubule-based mechanisms and DNA-based “tethers” connecting the acentric to the main chromosome mass are responsible for proper segregation of acentrics. In Chapter 2, we discuss the mechanisms by which acentric sister chromatids remain paired and eventually separate from one another during anaphase. Taking advantage of Drosophila transgenic for the I-CreI endonuclease, we efficiently generate broken chromosome fragments lacking centromeres, thereby lacking kinetochores. By using a genetic screen and live analysis, we identify proteins responsible for the separation of acentric chromosomes. We conclude DNA catenations are responsible for keeping acentric sisters paired and Topoisomerase II activity and microtubule plus-end pushing forces are needed to resolve these catenations and separate the acentrics. In Chapter 3, we highlight the remarkable ability of acentrics to congress to the metaphase plate despite the absence of kinetochore-microtubule interactions. Through mutational and live cell analysis, we define the forces acting on chromosome arms and the role of the kinetochore in chromosome congression. Utilizing Drosophila with fluorescently tagged acentric X chromosomes, we find acentric chromosome congression relies on interpolar microtubules as well as polar ejection forces. Our studies also show the induction of the DNA damage response leads to a global reorganization of congressed chromosomes at metaphase. Overall, this dissertation reveals a previously unsuspected kinetochore-independent backup mechanism by which chromosome fragments are able to progress normally through the initial stages of mitosis. Just as the discovery of cell cycle checkpoints led to new insights into the origins of cancer and novel therapies, it is likely that these and future insights into the transmission of chromosome fragments will have a similar impact on basic and applied cancer research.

Cells that divide with lagging chromosomes risk losing key genetic information if those chromosomes are not incorporated into daughter nuclei. When the nuclear envelope reforms a physical barrier around the daughter nucleus, lagging chromosomes are expected to be locked out of the nucleus and form damage-prone micronuclei. While micronuclei occur fairly frequently in cancer cells, lagging chromosomes can still sometimes enter telophase daughter nuclei to preserve euploidy. However, very little is known about the cellular mechanisms that allow lagging chromosomes to reintegrate into daughter nuclei and maintain genome integrity. In Drosophila, lagging chromosome fragments lacking a centromere, called acentrics, are capable of efficient reintegration into telophase daughter nuclei. Acentrics remain connected to daughter nuclei through a DNA tether. The tether is coated with Polo kinase, BubR1 kinase, Aurora B kinase, and INCENP, but the function of the tether is poorly understood. Here, I use Drosophila as a model system to identify mechanisms that promote lagging chromosome reintegration. I find that dividing with lagging chromosomes triggers the formation of highly localized gaps in the nascent nuclear envelope surrounding daughter nuclei. These gaps form channels through which acentrics pass to enter into daughter nuclei. Channel formation requires the pool of Aurora B kinase localized to the tether. Aurora B kinase phosphorylates chromatin on the acentric and at the site of acentric entry, keeping this chromatin in a mitotic state that prevents the recruitment of nuclear envelope components, leading to gap formation. Furthermore, I find that while acentrics are free of lamin and nuclear pore complexes, nuclear membrane frequently contacts acentrics during reintegration. Fusion between membrane on the acentric and membrane on the nucleus guides the acentric through the channel. The membrane fusion protein Comt/NSF and the ESCRT-III component Shurb/CHMP4B are required for these fusion events and efficient acentric entry into daughter nuclei. Taken together, these results uncover novel mechanisms by which lagging chromosomes can rejoin daughter nuclei to preserve the integrity of the genome.

A broad array of endosymbionts ensure their spread through host populations via vertical transmission, yet much remains unknown concerning the type and number of cellular mechanisms underlying reliable transmission. Wolbachia are the most common endosymbionts in nature, but their prevalence varies greatly in host populations due to imperfect transmission. To better understand the cellular basis of Wolbachia transmission, this project explored the cellular distributions of Wolbachia diverged up to 40 million years in the oocytes of 18 divergent Drosophila species. This analysis revealed three cellular distributions: 1) a tight clustering of Wolbachia at the posterior pole plasm (the site of germline formation); 2) a concentration at the posterior pole plasm, but with a significant population of Wolbachia distributed throughout the oocyte; 3) and a distribution of Wolbachia throughout the oocyte, with none or very few located at the posterior pole plasm. Examination of this latter class reveal Wolbachia access the posterior pole plasm during the interval between late oogenesis and the blastoderm formation. Wolbachia in this class concentrate in the posterior somatic follicle cells that encompass the pole plasm of the developing oocyte suggesting these are the source of that ultimately occupy the germline. In contrast, strains in which Wolbachia concentrate in the posterior pole plasm, no or few Wolbachia are found in the follicle cells associated with the pole plasm. Phylogenomic analysis indicates that closely related Wolbachia tend to exhibit similar patterns of posterior localization, suggesting that diverse localization strategies are a function of Wolbachia-associated factors. Previous studies revealed that endosymbionts rely on one of two distinct routes of vertical transmission: continuous maintenance in the germline (germline-to-germline) and a more circuitous route via the soma (germline-to-soma-to-germline). This work demonstrates that Wolbachia maintains the diverse arrays of cellular mechanisms necessary for both of these distinct transmission routes. This characteristic may account for its ability to infect and spread globally through a vast range of host insect species.

Accurate cell division is paramount to growth, development, and repair in all multi- cellular organisms. Unsurprisingly, cell division is highly regulated, with checkpoints in place following the major growth phase, DNA duplication, and spindle assembly. However, no checkpoint exists to determine whether or not the resulting daughters physically divide. It is on this process, cytokinesis, which serves as the focal point of my thesis.

Cytokinesis results in the physical separation of two daughter cells following mitosis. In animal cells, this process relies heavily on the contraction of the actomyosin ring at the ingressing furrow. Along with this mechanical pinching, cells rely on the addition of membrane components to the furrow to increase the membrane surface area of both daughters. New membrane is delivered via vesicles derived from both the secretory and endocytic pathways. Cytokinesis failure results in binucleate cells, which can lead to aneuploidy, a hallmark of cancer, or cell death in the following divisions.

Vesicle delivery must be highly regulated during cytokinesis. Because these vesicles function in other processes prior to mitosis, redirection and timing are everything. Our lab specifically focuses on the functional transition of the recycling pathway from interphase to mitosis in the early Drosophila embryo. During mitosis, the recycling endosome (RE) is positioned at the centrosomes and sends vesicles to the ingressing furrow. These vesicles contribute membrane, actin, and actin remodelers to the furrow, and mutants in major parts of this pathway result in incomplete ingression, aneuploidy, and failure of the embryo to develop. The primary focus of my thesis is the cell cycle regulation of RE-derived vesicle delivery to the ingressing furrow. Specifically, I examine the role of the conserved

Drosophila protein, Nuf, in regulating vesicle delivery during the early embryonic divisions and during the asymmetric stem cell divisions of the larval neuroblast.

Rab11 is a small RE-associated GTPase required for vesicle-mediated membrane delivery to the ingressing furrow. Nuf is a Rab11 effector that binds Rab11 GTP at the RE and is required to activate vesicle delivery. In the early embryo, without Nuf vesicle delivery is not initiated, leading to cytokinesis failure and embryonic lethality. However, Nuf localization to the centrosome must be regulated to occur only during mitosis. Indeed, we observe that Nuf localization is cell cycle-regulated, with its highest concentration at the centrosome occurring at prophase followed by loss of Nuf from the centrosome. Stimulation of the embryo by cyclin-B injection to jumpstart mitosis similarly displaces Nuf from the centrosome. We find that this localization correlates with high phosphorylation levels of Nuf shortly following its cytoplasmic dispersal. This is achieved through phosphorylation of Ser225 and Thr227 specifically by the cell cycle kinase Polo. In vivo, inhibition of Polo activity results in a loss of phosphorylated Nuf as well as Nuf maintenance at the centrosome during metaphase, when it should have already dispersed to the cytoplasm. Constitutive activation of Polo showed an opposing effect, with less Nuf at the centrosome even during prophase, though these results were not significant.

As we probed further into the importance of Nuf phosphorylation, we generated non- phosphorylatable and phosphomimetic Nuf mutants to determine whether these two residues alone are responsible for the localization defects observed in the different polo backgrounds. It is important to parse these differences, as Polo plays several roles during the cell cycle that may directly influence Nuf localization. While non-phospho Nuf did not have an observable effect on Nuf localization, phosphomimetic Nuf was not maintained at the centrosome at any phase of mitosis. Further, both mutants exhibited furrowing defects in the form of actin gaps and ectopic actin. These results strongly suggest phosphorylation of these residues specifically plays a key role in Nuf localization and activity during cytokinesis.

Nuf localization to the centrosome is driven by the minus-end directed motor, Dynein/Dynactin and dependent on microtubules. Indeed inhibition of microtubule polymerization or Dynein heavy chain expression prevents Nuf accumulation at the

centrosome regardless of mitotic phase. Cytoplasmic Nuf binds Dynein/Dynactin and is transported along the microtubules to the centrosome-associated RE. Nuf is continually dispersing from the RE into the cytoplasm, requiring constant recruitment via Dynein/Dynactin until metaphase. We hypothesize that phosphorylation of Nuf at these residues disrupts the Nuf/Dynein binding site. These residues lie outside of the Rab11- binding domain, suggesting another mechanism for Nuf loss from the centrosome when it is phosphorylated. Nuf has been shown to bind both Dynein heavy chain as well as a component of the dynactin complex, Arp1. In a dosage-sensitive interaction between nuf and Dynein/Dynactin components, flies heterozygous for nuf and dynactin 2 are semi-sterile, suggesting a strong interaction. Further work is required to determine whether these mutant residues are capable of binding Dynein/Dynactin directly.

In addition to its role in cytokinesis regulation in the early embryo, we examined a potential role for Nuf in regulating division asymmetry later in development. Division asymmetry is controlled by many factors intrinsic and extrinsic to the cell. Many early studies demonstrate the importance of proper segregation of small RNA and protein determinants to specific regions of the cell cortex. Additionally, the centrosome has been shown to influence division asymmetry in several cell types and organism. Much like the cortical determinants, inheritance of the mother or daughter centrosome is specified to the daughter stem cell faithfully in each division. Recently, we learned that exogenous formation of an active RE in Drosophila sensory organ precursor (SOP) cells increases cell fate transformation. Using our developed tools for RE examination and manipulation, we sought to determine how Nuf expression affects the asymmetric divisions of the Drosophila larval neuroblast (NB) and pupal SOP cells.

The Drosophila larval neuroblast is a neural stem cell that produces a population of differentiated neurons that comprise much of the adult central nervous system. It divides asymmetrically into a self-renewing daughter neuroblast and a differentiating ganglion mother cell (GMC). In this division, the daughter centrosome is preferentially segregated to the self-renewing daughter NB. We find that Nuf is also preferentially segregated to the daughter NB following division. Expression of our Nuf phospho-mutants maintains this preference, in which both non-phospho and phosphomimetic Nuf are more frequently inherited by the daughter NB. Interestingly, when Nuf is symmetrically distributed following division, non-phospho Nuf is frequently lost from both daughters following division, while phosphomimetic Nuf is maintained in both daughters. We hypothesize that phosphorylation of Nuf may protect it from degradation during division. Polo, a known kinase of Nuf, is repressed in the daughter GMC, while its activity is enhanced in the daughter NB. This provides a model in which Polo phosphorylates Nuf in the daughter NB, while any Nuf remaining in the daughter GMC is targeted for degradation.

Drosophila SOP cells divide asymmetrically to expand the peripheral nervous system including the bristles, socket cells, sensory neurons, and sheath cells. Following the first division, only one of the daughter cells (pIIb) forms an active RE. Overexpression of both Rab11 and Nuf result in RE formation in both pIIb and pIIa daughters, and this leads to cell fate transformations toward the epithelial fate that manifest as bristle duplications. We find that expression of phosphomimetic Nuf, but not non-phospho nor GFP Nuf, in SOP cells results in statistically significant bristle duplications. We hypothesize that phosphorylation of Nuf stabilizes the RE in SOP cells, resulting in RE formation in pIIb and pIIa, driving a preference for epithelial fate.

Altogether, this thesis explores the role of the RE-associated protein Nuf in the regulation of RE throughout development in Drosophila. Nuf influences and directly regulates cytokinesis in the early embryo via RE-derived vesicle delivery to the ingressing furrow. Nuf phosphorylation influences its subcellular localization and stabilization in the embryo, larval neuroblast, and sensory organ precursor cells.

Unrepaired double strand DNA breaks can have deleterious consequences at mitosis due to the generation of acentric chromosome fragments that lack centromeres. Although acentrics are common in cancer cells, surprisingly little is known about the mechanisms regulating kinetochore-independent chromosome segregation. Acentrics are efficiently induced in Drosophila neuroblasts by expressing an endonuclease called I-CreI. Previous reports in Drosophila have found that while acentrics lack a kinetochore, they still move to the metaphase plate and segregate to daughter cells. The delayed but ultimately successful segregation of acentrics requires a chromatin tether that connects the acentrics to the main chromosome mass. The tethers are decorated with BubR1, Aurora B and Polo kinases. Disruptions in BubR1 and Polo functions led to defects in acentric segregation and a decreased rate of survival from larvae into adulthood (synthetic lethality). This led to the conclusion that the tether provides the driving force for acentric segregation. Here, I demonstrate that acentrics are preferentially bundled with microtubules during anaphase suggesting that microtubules and motor proteins exert the force for driving acentric segregation. Interestingly, the orientation of acentrics during anaphase is random with half the acentrics segregating telomere first (telomere facing pole), while the other half segregates telomere last (telomere facing metaphase plate). This is in accord with a model in which acentrics behave as cargo capable of associating in any orientation with microtubules. By conducting a synthetic lethality screen, I found that I-CreI expressing larvae with disruptions in Klp3a, which encodes for a chromosome and microtubule-associated motor protein (chromokinesin) led to an increased rate of synthetic lethality. Through live imaging, I found defects in acentric segregation in neuroblast depleted of Klp3a. Taken together, these results suggest that the cell maintains a microtubule and Kp3a dependent mechanism to drive acentric segregation.

Delayed acentric segregation during anaphase raises the question of how acentrics affect nuclear envelope reformation (NER). Here I demonstrate that acentrics enter daughter nuclei by inducing a local delay in NER, which leads to the formation of a channel in the nuclear envelope. The formation of the nuclear envelope channels is dependent on Aurora B kinase.

The cytoskeleton plays a variety of roles during the cell cycle, none more dramatic than the formation of a bipolar mitotic spindle and the subsequent cleavage of one cell into two. Proper centrosome separation is a prerequisite for positioning the bipolar spindle. Although studies demonstrate that microtubules and their associated motors drive centrosome separation, the role of actin in centrosome separation remains less clear. Studies in tissue culture cells indicate that actin- and myosin-based cortical flow is primarily responsible for driving late centrosome separation, whereas other studies suggest that actin plays a more passive role by serving as an attachment site for astral microtubules to pull centrosomes apart. Here we demonstrate that prior to nuclear envelope breakdown (NEB) in Drosophila embryos; proper centrosome separation does not require myosin II but requires dynamic actin rearrangements at the growing edge of the interphase cap. Both Arp2/3- and Formin-mediated actin remodeling are required for separating the centrosome pairs before NEB. The Apc2-Armadillo complex appears to link cap expansion to centrosome separation. In contrast, the mechanisms driving centrosome separation after NEB are dependent of the actin cytoskeleton and compensate for earlier separation defects. Our studies show that the dynamics of actin polymerization drive centrosome separation and this has important implications for centrosome positioning during processes such as cell migration, cell polarity maintenance, and asymmetric cell division.

Another vital role for spindle formation is in positioning the site of cleavage following anaphase separation of DNA. Rappaport's experiments with sand dollar embryos showed that cleavage furrow positioning is determined by the relationship between the spindle and the actin cortex. In his embryos, astral microtubules, which extend out to the cortex were primarily responsible for initiating a furrow, however, smaller somatic cells seem to position the furrow through the overlapping antiparallel central spindle. This balance between astral and central spindle influences is not well understood however. In the early Drosophila embryo, nuclei divide within a syncytium yet invaginate cortical actin and membrane, encompassing them, in order to complete mitosis in close proximity to neighboring nuclei. These furrows are considered natural Rappaport furrows since they form at astral microtubule overlap. Upon cellularization, the furrow positioning seems to shift from astral microtubule-based to central spindle-based. Our findings show that during the syncytial divisions, key conserved central spindle components Centralspindlin complex, Polo, and Fascetto (Prc1) all localize to regions of overlap astral microtubules during furrow formation. Given that the central spindle does not induce formation of conventional cytokinesis, finding that all of these components, plus the chromosomal passenger complex (Aurora B and INCENP), also localize to the central spindle was unexpected. The lack of furrow formation at the central spindle then is explained by the fact that the syncytial divisions rely on a maternally supplied form of RhoGEF, RhoGEF2, lacking the specific domains that localize zygotically expressed RhoGEF (Pebble) to the central spindle. RhoGEF2 instead localizes to the overlap astral microtubules of the syncytial divisions. Thus, in spite of proper localization of many key furrowing components to the central spindle in syncytial embryos, the failure of RhoGEF to localize to the central spindle may preclude formation of conventional cleavage furrows bisecting the spindle. In support of this idea, we bypass the need for RhoGEF by injecting constitutively active Rho into the syncytial embryos. This generates ectopic furrows strikingly similar to conventional cleavage furrows that form perpendicular to the central spindle during the syncytial divisions. While metaphase furrow formation is myosin independent these Rho-induced ectopic furrows, like conventional furrows, require myosin in addition to microtubules. These studies demonstrate that the early Drosophila embryo is primed to form furrows at either the overlapping astral microtubules or central spindle with the shift to the latter being driven in large part by a corresponding shift from maternal-to-zygotic forms of RhoGEF.

My studies predict that the delivery of RhoGEF2 to the metaphase furrows must be different than the mechanism that localizes Pebble to the central spindle (the Centralspindlin complex). Recently, it has been shown that RhoGEF2 localization to the metaphase furrows requires vesicle trafficking from the recycling endosome (RE). This vesicle trafficking is regulated by the Rab11-GTPase in the RE and its associated effector, Nuclear Fallout (Nuf). Previous observations of Nuf in the early embryo show that it accumulates at the RE from interphase to prophase during the time when furrows are being made. At prophase, Nuf is phosphorylated, which coincides with its diffusion away from the RE. I will present evidence that Nuf localization is regulated by its phosphorylation state and that the mitotic kinase, Polo directly phosphorylates Nuf, inhibiting its localization at the RE, decreasing vesicle trafficking to the furrow. I propose that this mechanism serves as a major component in timing the formation of a furrow and may provide valuable insight into timing cytokinesis in general.

Finally, the regulation of actin dynamics in cytokinesis has been well studied in terms of actin-interacting proteins such as Cofilin and Profilin. However, the direct modifications of actin and microtubules are similarly important for stable furrow ingression and abscission. Here I will present a newly characterized gene push pop that potentially indicates methylation of actin or tubulin as a previously unappreciated mechanism of regulating the cytoskeleton as well as other potential mitotic proteins in the events of cytokinesis.

The thesis work presented here promotes a broader understanding of cytokinetic furrow timing and positioning. On one hand, both centrosome separation and central spindle signaling are vital for proper furrow positioning. On the other hand, vesicle trafficking and folate metabolism are required for the proper timing and maintenance of a furrow during the cell cycle. A deeper understanding of both these processes of cytokinesis will provide valuable insight into the mechanisms of cell division and potentially how they are perturbed in tumorigenesis.

Wolbachia are gram-negative, obligate, intracellular bacteria infecting a majority of insect species and filarial nematodes. In both insects and nematodes Wolbachia are primarily transmitted through the female germ line. Wolbachia carried by filarial nematodes are the cause of the neglected diseases African river blindness and lymphatic filariasis afflicting millions worldwide. In order to combat these diseases, we created a Wolbachia-infected Drosophila cell line that enabled high throughput screening for novel potent anti-Wolbachia compounds. Of the 36,231 compounds screened in house, 8 compounds dramatically reduced Wolbachia titer both in the cell and nematode based screen. Significantly, we discovered that the albendazole metabolite, albendazole sulfone, reduces Wolbachia titer in Drosophila melanogaster and the filarial nematode Brugia malayi perhaps by directly targeting Wolbachia FtsZ. Using the Wolbachia-infected cell line, we discovered that in addition to vertical germ line transmission, Wolbachia are efficiently transmitted horizontally via cell-to-cell transmission. We show that horizontal transfer is independent of cell-to-cell contact, can efficiently take place within hours, and uses both host cell phagocytic and clathrin/dynamin-dependent endocytic machinery. Modifications to our high-throughput screen in combination with genome-wide RNA interference (RNAi) identified host factors that influence Wolbachia titer. When these host factors were tested in Drosophila melanogaster in vivo we found that maintenance of Wolbachia titer relies on an intact host Endoplasmic Reticulum (ER) associated degradation (ERAD) system. These data, in combination with electron microscopy studies, demonstrated that Wolbachia is intimately associated with the host ER and suggested a previously unsuspected mechanism for the potent ability of Wolbachia to prevent RNA virus replication. To examine the impact of nutritional on Wolbachia titer, Drosophila were fed sucrose- and yeast-enriched diets. These conditions resulted in increased and decreased Wolbachia titer in Drosophila oogenesis, respectively, and that somatic TOR and insulin signaling mediate the response of the yeast-enriched diet on Wolbachia. Taken together, these studies provide initial insights into the molecular and cellular interactions between Wolbachia and its insect and nematode hosts.

Filarial nematodes are human parasites that infect millions of people across the globe and cause debilitating diseases such as Elephantiasis and African River Blindness. These worms share a symbiotic relationship with Wolbachia, an obligate, alpha-proteobacteria endosymbiont, and rely on these bacteria for survival and proper embryogenesis. Taking advantage of this crucial symbiosis, efforts to identify drugs that kill the adult worm by targeting Wolbachia have proven to be promising. Here, I describe the discovery and optimization of quinazolines CBR417 and CBR490 that, with a single dose, achieve >99% elimination of Wolbachia in the in vivo Litomosoides sigmodontis filarial infection model. These potent quinazolines were identified by pairing a primary cell-based high-throughput imaging screen with a secondary ex vivo validation assay to rapidly quantify Wolbachia elimination in Brugia pahangi filarial ovaries. To better understand the relationship between Wolbachia and its worm host, adult Brugia pahangi were exposed to varying concentrations of common antibiotics in vitro and assessed for Wolbachia numbers in the germline tissue. Surprisingly, we found that worms treated with higher concentrations of antibiotics had higher Wolbachia titers, and antibiotics given at low concentrations reduced Wolbachia titers. This counterintuitive dose response is known as the “Eagle effect” and the presence of this effect in Wolbachia suggests a common underlying mechanism that allows diverse bacterial and fungal species to persist despite exposure to high concentrations of antimicrobial compounds. To our knowledge this is the first report of this phenomenon occurring in an intracellular endosymbiont, Wolbachia, in its filarial host. While several studies have shown that novel and FDA-approved antibiotics are efficacious at depleting the filarial nematodes of their endosymbiont, thus reducing female fecundity, it remains unclear if antibiotics can permanently deplete Wolbachia and cause sterility for the lifespan of the adult worms. We investigated the long-term effects of the antibiotic, rifampicin, in the Brugia pahangi jird model of infection. Initially, rifampicin treatment depleted Wolbachia in adult worms and simultaneously impaired female worm fecundity. However, during an 8-month washout period, Wolbachia titers rebounded and embryogenesis returned to normal. Clusters of densely packed Wolbachia within the worm’s ovarian tissues were observed by confocal microscopy. The number, size, and Wolbachia density of these clusters were not diminished despite large doses of rifampicin antibiotic. This finding suggests that these clusters may serve as privileged sites that allow Wolbachia to persist in worms while treated with antibiotic. Lastly, I define the cellular characteristics of these clusters, which fit the definition of endosymbiont bacteriocytes, and I identify drugs that target them. Nascent bacteriocytes arise in newly formed sheath cells adjacent to the distal tip cell of the Brugia pahangi germline. They dramatically enlarge but do not appear to disrupt the integrity of the sheath cells. We determined that the Wolbachia within bacteriocytes are either in a quiescent form or replicating at a very low rate. These Wolbachia-based bacteriocytes are present in Brugia malayi, one of the nematode species which cause human filariasis, as well as B. pahangi. Screens of known antibiotics and other drugs revealed two drugs, Fexinidazole and Corallopyronin A, have strong anti-bacteriocyte efficacy.