Joshua Thomson - Academia.edu (original) (raw)
Papers by Joshua Thomson
Education Research International, 2022
Objectives. The March 2020 lockdown mandated institution closures and forced educators to provide... more Objectives. The March 2020 lockdown mandated institution closures and forced educators to provide remote instruction. We intended to gain an in-depth and holistic understanding of dental faculty’s experience and perceptions during this mandatory shift. Insights were gathered in 6 key areas: prior remote instruction experience; magnitude of transition and frequency of instruction methods used; training received; preferred teaching methods based on how they promote student learning, interaction, engagement, and performance; social impact; and future of teaching. Methods. An anonymous QualtricsXM survey was distributed to all dental faculties at University of Detroit Mercy in May 2020. Data was collected over a three-week period and analyzed using Statistical Package for the Social Sciences (SPSS) Statistics 26 (IBM; Armonk, New York, USA). Pearson chi-squared test and Fisher’s exact test were used to evaluate categorical data. Results. Out of the 30 participants who transitioned to on...
The Angle Orthodontist, 2021
Objectives To evaluate the ability of different esthetic archwires to retain oral biofilms in vit... more Objectives To evaluate the ability of different esthetic archwires to retain oral biofilms in vitro. Materials and Methods Seven different brands of coated orthodontic archwires were tested: two epoxy coated, two polytetrafluoroethylene coated, two rhodium coated, and one silver plus polymer coated. Conventional uncoated metallic archwires were used as controls. Streptococus mutans adherence to archwires was quantified by colony count following 24 hours of biolfilm growth, and total wire-associated biofilm was measured using a crystal violet staining assay. For both tests, two conditions were used: 0% sucrose and 3% sucrose. For statistical analysis, P < .05 was considered as statistically significant. Results For S. mutans colony forming units per biofilm, there were no statistically significant differences among the various archwires (P = .795 for 0% sucrose; P = .905 for 3% sucrose). Regarding total biofilm formed on archwires in the 3% sucrose condition, there were statistica...
International Journal of Environmental Research and Public Health, 2022
To improve oral hygiene education, we evaluated the perception and potential impact of microbiolo... more To improve oral hygiene education, we evaluated the perception and potential impact of microbiology-focused oral hygiene instructions (OHI) given to pregnant patients. Dental hygienists provided this supplemental education and administered Saliva-Check Mutans (SCM) tests to pregnant patients (n = 188) in Obstetrics and Gynecology (OB/GYN) settings. Patients reported their self-perceived understanding of the relationship between oral bacteria and dental disease and returned postdelivery to receive a second SCM test and follow-up questionnaire (n = 47). Prior to the hygienist instruction, 84% of participants understood that bacteria caused tooth decay, while only 36% understood they could transfer these bacteria to their children. After instruction, patient understanding increased to 97% and 95%, respectively. Participants attributed these increases to the hygienist’s explanation and SCM test. In postdelivery participants, >80% reported adherence to routine oral hygiene practices, ...
FEBS Letters
Pathogens that colonize deep tissues and spread systemically encounter the innate host resistance... more Pathogens that colonize deep tissues and spread systemically encounter the innate host resistance mechanism of complement-mediated lysis and complement opsonization leading to engulfment and degradation by phagocytic cells. Yersinia and Salmonella species have developed numerous strategies to block the antimicrobial effects of complement. These include recruitment of complement regulatory proteins factor H, C4BP, and vitronectin (Vn) as well as interference in late maturation events such as assembly of C9 into the membrane attack complex that leads to bacterial lysis. This review will discuss the contributions of various surface structures (proteins, lipopolysaccharide, and capsules) to evasion of complement-mediated immune clearance of the systemic pathogens Yersiniae and Salmonellae. Bacterial proteins required for recruitment of complement regulatory proteins will be described, including the details of their interaction with host regulatory proteins, where known. The potential role of the surface proteases Pla (Yersinia pestis) and PgtE (Salmonella species) on the activity of complement regulatory proteins will also be addressed. Finally, the implications of complement inactivation on host cell interactions and host cell targeting for type 3 secretion will be discussed.
Molecular Microbiology
Ail, a multifunctional outer membrane protein of Yersinia pestis, confers cell binding, Yop deliv... more Ail, a multifunctional outer membrane protein of Yersinia pestis, confers cell binding, Yop delivery and serum resistance activities. Resistance to complement proteins in serum is critical for the survival of Y. pestis during the septicemic stage of plague infections. Bacteria employ a variety of tactics to evade the complement system, including recruitment of complement regulatory factors, such as factor H, C4b-binding protein (C4BP) and vitronectin (Vn). Y. pestis Ail interacts with the regulatory factors Vn and C4BP, and Ail homologs from Y. enterocolitica and Y. pseudotuberculosis recruit factor H. Using co-sedimentation assays, we demonstrate that two surface-exposed amino acids, F80 and F130, are required for the interaction of Y. pestis Ail with Vn, factor H and C4BP. However, although Ail-F80A/F130A fails to interact with these complement regulatory proteins, it still confers 10,000-fold more serum resistance than a Δail strain and prevents C9 polymerization, potentially by directly interfering with MAC assembly. Using site-directed mutagenesis, we further defined this additional mechanism of complement evasion conferred by Ail. Finally, we find that at Y. pestis concentrations reflective of early-stage septicemic plague, Ail weakly recruits Vn and fails to recruit factor H, suggesting that this alternative mechanism of serum resistance may be essential during plague infection.
Genome announcements, Jan 26, 2017
Seven mycobacteriophages from distinct geographical locations were isolated, using Mycobacterium ... more Seven mycobacteriophages from distinct geographical locations were isolated, using Mycobacterium smegmatis mc2155 as the host, and then purified and sequenced. All of the genomes are related to cluster A mycobacteriophages, BobSwaget and Lokk in subcluster A2; Fred313, KADY, Stagni, and StepMih in subcluster A3; and MyraDee in subcluster A18, the first phage to be assigned to that subcluster.
Infection and immunity, Jan 6, 2017
Yersinia pestis, the causative agent of plague, binds host cells to deliver cytotoxic Yop protein... more Yersinia pestis, the causative agent of plague, binds host cells to deliver cytotoxic Yop proteins into the cytoplasm that prevent phagocytosis and generation of pro-inflammatory cytokines. Ail is an eight-stranded β-barrel outer membrane protein with four extracellular loops that mediates cell binding and resistance to human serum. Following deletion of each of the four extracellular loops that potentially interact with host cells, the Ail-Δloop 2 and Ail-Δloop 3 mutants had no cell binding activity while Ail-Δloop 4 maintained cell binding (the Ail-Δloop 1 protein was unstable). Using the codon mutagenesis scheme SWIM (Selection Without Isolation of Mutants) we identified individual residues in loops 1-3 that contribute to host cell binding. While several residues contributed to binding host cells, purified fibronectin, laminin and Yop delivery, three mutants, F80A (loop 2), S128A (loop 3) and F130A (loop 3), had particularly severe defects in cell binding. Combining these mutatio...
Dr. Judith Whittum-Hudson. I would like to thank them all for the support they have provided. Add... more Dr. Judith Whittum-Hudson. I would like to thank them all for the support they have provided. Additional support came from the members, past and present, of the Withey lab. All members were important in scientific discussion and made the lab enjoyable. Basel Abuaita and Michelle Bellair trained me in the lab and without them I would not have been as successful. I will carry their work ethic with me throughout my career. Additionally, I would like to thank
Journal of bacteriology, Jan 16, 2015
TcpP and ToxR coordinately regulate transcription of toxT, the master regulator of numerous virul... more TcpP and ToxR coordinately regulate transcription of toxT, the master regulator of numerous virulence factors in Vibrio cholerae. TcpP and ToxR are membrane-localized transcription factors each with a periplasmic domain containing two cysteines. In ToxR these cysteines form an intramolecular disulfide bond and a cysteine to serine substitution affects activity. We determined that the two periplasmic cysteines of TcpP also form an intramolecular disulfide bond. Disruption of this intramolecular disulfide bond by mutation of either cysteine resulted in formation of intermolecular disulfide bonds. Furthermore, disruption of the intramolecular disulfide bond in TcpP decreased the stability of TcpP. While the decreased stability of TcpP-C207S resulted in a nearly complete loss of toxT activation and cholera toxin (CT) production, the second cysteine mutant, TcpP-C218S, was partially resistant to proteolytic degradation and maintained ∼50% toxT activation capacity. TcpP-C218S was also Tcp...
Journal of Bacteriology, 2014
The major Vibrio cholerae virulence gene transcription activator, ToxT, is responsible for the pr... more The major Vibrio cholerae virulence gene transcription activator, ToxT, is responsible for the production of the diarrhea-inducing cholera toxin (CT) and the major colonization factor, toxin coregulated pilus (TCP). In addition to the two primary virulence factors mentioned, ToxT is responsible for the activation of accessory virulence genes, such as aldA , tagA , acfA , acfD , tcpI , and tarAB . ToxT activity is negatively modulated by bile and unsaturated fatty acids found in the upper small intestine. Conversely, previous work identified another intestinal signal, bicarbonate, which enhances the ability of ToxT to activate production of CT and TCP. The work presented here further elucidates the mechanism for the enhancement of ToxT activity by bicarbonate. Bicarbonate was found to increase the activation of ToxT-dependent accessory virulence promoters in addition to those that produce CT and TCP. Bicarbonate is taken up into the V. cholerae cell, where it positively affects ToxT ...
Journal of Bacteriology, 2014
Vibrio choleraeis the causative agent of the severe diarrheal disease cholera. The production of ... more Vibrio choleraeis the causative agent of the severe diarrheal disease cholera. The production of the virulence factors that are required for human disease is controlled by a complex network of transcriptional and posttranscriptional regulators. ToxT is the transcription regulator that directly controls the production of the two major virulence factors, toxin-coregulated pilus (TCP) and cholera toxin (CT). The solved crystal structure of ToxT revealed an unstructured region in the N-terminal domain between residues 100 and 110. This region and the surrounding amino acids have been previously implicated in ToxT proteolysis, resistance to inhibition by negative effectors, and ToxT dimerization. To better characterize this region, site-directed mutagenesis was performed to assess the effects on ToxT proteolysis and bile sensitivity. This analysis identified specific mutations within this unstructured region that prevent ToxT proteolysis and other mutations that reduce inhibition by bile...
Journal of Bacteriology, Nov 24, 2014
Vibrio cholerae is the causative agent of the severe diarrheal disease cholera. The production of... more Vibrio cholerae is the causative agent of the severe diarrheal disease cholera. The production of the virulence factors that are required for human disease is controlled by a complex network of transcriptional and posttranscriptional regulators. ToxT is the transcription regulator that directly controls the production of the two major virulence factors, toxin-coregulated pilus (TCP) and cholera toxin (CT). The solved crystal structure of ToxT revealed an unstructured region in the N-terminal domain between residues 100 and 110. This region and the surrounding amino acids have been previously implicated in ToxT proteolysis, resistance to inhibition by negative effectors, and ToxT dimerization. To better characterize this region, site-directed mutagenesis was performed to assess the effects on ToxT proteolysis and bile sensitivity. This analysis identified specific mutations within this unstructured region that prevent ToxT proteolysis and other mutations that reduce inhibition by bile and unsaturated fatty acids. In addition, we found that mutations that affect the sensitivity of ToxT to bile also affect the sensitivity of ToxT to its positive effector, bicarbonate. These results suggest that a small unstructured region in the ToxT N-terminal domain is involved in multiple aspects of virulence gene regulation and response to human host signals.
Education Research International, 2022
Objectives. The March 2020 lockdown mandated institution closures and forced educators to provide... more Objectives. The March 2020 lockdown mandated institution closures and forced educators to provide remote instruction. We intended to gain an in-depth and holistic understanding of dental faculty’s experience and perceptions during this mandatory shift. Insights were gathered in 6 key areas: prior remote instruction experience; magnitude of transition and frequency of instruction methods used; training received; preferred teaching methods based on how they promote student learning, interaction, engagement, and performance; social impact; and future of teaching. Methods. An anonymous QualtricsXM survey was distributed to all dental faculties at University of Detroit Mercy in May 2020. Data was collected over a three-week period and analyzed using Statistical Package for the Social Sciences (SPSS) Statistics 26 (IBM; Armonk, New York, USA). Pearson chi-squared test and Fisher’s exact test were used to evaluate categorical data. Results. Out of the 30 participants who transitioned to on...
The Angle Orthodontist, 2021
Objectives To evaluate the ability of different esthetic archwires to retain oral biofilms in vit... more Objectives To evaluate the ability of different esthetic archwires to retain oral biofilms in vitro. Materials and Methods Seven different brands of coated orthodontic archwires were tested: two epoxy coated, two polytetrafluoroethylene coated, two rhodium coated, and one silver plus polymer coated. Conventional uncoated metallic archwires were used as controls. Streptococus mutans adherence to archwires was quantified by colony count following 24 hours of biolfilm growth, and total wire-associated biofilm was measured using a crystal violet staining assay. For both tests, two conditions were used: 0% sucrose and 3% sucrose. For statistical analysis, P < .05 was considered as statistically significant. Results For S. mutans colony forming units per biofilm, there were no statistically significant differences among the various archwires (P = .795 for 0% sucrose; P = .905 for 3% sucrose). Regarding total biofilm formed on archwires in the 3% sucrose condition, there were statistica...
International Journal of Environmental Research and Public Health, 2022
To improve oral hygiene education, we evaluated the perception and potential impact of microbiolo... more To improve oral hygiene education, we evaluated the perception and potential impact of microbiology-focused oral hygiene instructions (OHI) given to pregnant patients. Dental hygienists provided this supplemental education and administered Saliva-Check Mutans (SCM) tests to pregnant patients (n = 188) in Obstetrics and Gynecology (OB/GYN) settings. Patients reported their self-perceived understanding of the relationship between oral bacteria and dental disease and returned postdelivery to receive a second SCM test and follow-up questionnaire (n = 47). Prior to the hygienist instruction, 84% of participants understood that bacteria caused tooth decay, while only 36% understood they could transfer these bacteria to their children. After instruction, patient understanding increased to 97% and 95%, respectively. Participants attributed these increases to the hygienist’s explanation and SCM test. In postdelivery participants, >80% reported adherence to routine oral hygiene practices, ...
FEBS Letters
Pathogens that colonize deep tissues and spread systemically encounter the innate host resistance... more Pathogens that colonize deep tissues and spread systemically encounter the innate host resistance mechanism of complement-mediated lysis and complement opsonization leading to engulfment and degradation by phagocytic cells. Yersinia and Salmonella species have developed numerous strategies to block the antimicrobial effects of complement. These include recruitment of complement regulatory proteins factor H, C4BP, and vitronectin (Vn) as well as interference in late maturation events such as assembly of C9 into the membrane attack complex that leads to bacterial lysis. This review will discuss the contributions of various surface structures (proteins, lipopolysaccharide, and capsules) to evasion of complement-mediated immune clearance of the systemic pathogens Yersiniae and Salmonellae. Bacterial proteins required for recruitment of complement regulatory proteins will be described, including the details of their interaction with host regulatory proteins, where known. The potential role of the surface proteases Pla (Yersinia pestis) and PgtE (Salmonella species) on the activity of complement regulatory proteins will also be addressed. Finally, the implications of complement inactivation on host cell interactions and host cell targeting for type 3 secretion will be discussed.
Molecular Microbiology
Ail, a multifunctional outer membrane protein of Yersinia pestis, confers cell binding, Yop deliv... more Ail, a multifunctional outer membrane protein of Yersinia pestis, confers cell binding, Yop delivery and serum resistance activities. Resistance to complement proteins in serum is critical for the survival of Y. pestis during the septicemic stage of plague infections. Bacteria employ a variety of tactics to evade the complement system, including recruitment of complement regulatory factors, such as factor H, C4b-binding protein (C4BP) and vitronectin (Vn). Y. pestis Ail interacts with the regulatory factors Vn and C4BP, and Ail homologs from Y. enterocolitica and Y. pseudotuberculosis recruit factor H. Using co-sedimentation assays, we demonstrate that two surface-exposed amino acids, F80 and F130, are required for the interaction of Y. pestis Ail with Vn, factor H and C4BP. However, although Ail-F80A/F130A fails to interact with these complement regulatory proteins, it still confers 10,000-fold more serum resistance than a Δail strain and prevents C9 polymerization, potentially by directly interfering with MAC assembly. Using site-directed mutagenesis, we further defined this additional mechanism of complement evasion conferred by Ail. Finally, we find that at Y. pestis concentrations reflective of early-stage septicemic plague, Ail weakly recruits Vn and fails to recruit factor H, suggesting that this alternative mechanism of serum resistance may be essential during plague infection.
Genome announcements, Jan 26, 2017
Seven mycobacteriophages from distinct geographical locations were isolated, using Mycobacterium ... more Seven mycobacteriophages from distinct geographical locations were isolated, using Mycobacterium smegmatis mc2155 as the host, and then purified and sequenced. All of the genomes are related to cluster A mycobacteriophages, BobSwaget and Lokk in subcluster A2; Fred313, KADY, Stagni, and StepMih in subcluster A3; and MyraDee in subcluster A18, the first phage to be assigned to that subcluster.
Infection and immunity, Jan 6, 2017
Yersinia pestis, the causative agent of plague, binds host cells to deliver cytotoxic Yop protein... more Yersinia pestis, the causative agent of plague, binds host cells to deliver cytotoxic Yop proteins into the cytoplasm that prevent phagocytosis and generation of pro-inflammatory cytokines. Ail is an eight-stranded β-barrel outer membrane protein with four extracellular loops that mediates cell binding and resistance to human serum. Following deletion of each of the four extracellular loops that potentially interact with host cells, the Ail-Δloop 2 and Ail-Δloop 3 mutants had no cell binding activity while Ail-Δloop 4 maintained cell binding (the Ail-Δloop 1 protein was unstable). Using the codon mutagenesis scheme SWIM (Selection Without Isolation of Mutants) we identified individual residues in loops 1-3 that contribute to host cell binding. While several residues contributed to binding host cells, purified fibronectin, laminin and Yop delivery, three mutants, F80A (loop 2), S128A (loop 3) and F130A (loop 3), had particularly severe defects in cell binding. Combining these mutatio...
Dr. Judith Whittum-Hudson. I would like to thank them all for the support they have provided. Add... more Dr. Judith Whittum-Hudson. I would like to thank them all for the support they have provided. Additional support came from the members, past and present, of the Withey lab. All members were important in scientific discussion and made the lab enjoyable. Basel Abuaita and Michelle Bellair trained me in the lab and without them I would not have been as successful. I will carry their work ethic with me throughout my career. Additionally, I would like to thank
Journal of bacteriology, Jan 16, 2015
TcpP and ToxR coordinately regulate transcription of toxT, the master regulator of numerous virul... more TcpP and ToxR coordinately regulate transcription of toxT, the master regulator of numerous virulence factors in Vibrio cholerae. TcpP and ToxR are membrane-localized transcription factors each with a periplasmic domain containing two cysteines. In ToxR these cysteines form an intramolecular disulfide bond and a cysteine to serine substitution affects activity. We determined that the two periplasmic cysteines of TcpP also form an intramolecular disulfide bond. Disruption of this intramolecular disulfide bond by mutation of either cysteine resulted in formation of intermolecular disulfide bonds. Furthermore, disruption of the intramolecular disulfide bond in TcpP decreased the stability of TcpP. While the decreased stability of TcpP-C207S resulted in a nearly complete loss of toxT activation and cholera toxin (CT) production, the second cysteine mutant, TcpP-C218S, was partially resistant to proteolytic degradation and maintained ∼50% toxT activation capacity. TcpP-C218S was also Tcp...
Journal of Bacteriology, 2014
The major Vibrio cholerae virulence gene transcription activator, ToxT, is responsible for the pr... more The major Vibrio cholerae virulence gene transcription activator, ToxT, is responsible for the production of the diarrhea-inducing cholera toxin (CT) and the major colonization factor, toxin coregulated pilus (TCP). In addition to the two primary virulence factors mentioned, ToxT is responsible for the activation of accessory virulence genes, such as aldA , tagA , acfA , acfD , tcpI , and tarAB . ToxT activity is negatively modulated by bile and unsaturated fatty acids found in the upper small intestine. Conversely, previous work identified another intestinal signal, bicarbonate, which enhances the ability of ToxT to activate production of CT and TCP. The work presented here further elucidates the mechanism for the enhancement of ToxT activity by bicarbonate. Bicarbonate was found to increase the activation of ToxT-dependent accessory virulence promoters in addition to those that produce CT and TCP. Bicarbonate is taken up into the V. cholerae cell, where it positively affects ToxT ...
Journal of Bacteriology, 2014
Vibrio choleraeis the causative agent of the severe diarrheal disease cholera. The production of ... more Vibrio choleraeis the causative agent of the severe diarrheal disease cholera. The production of the virulence factors that are required for human disease is controlled by a complex network of transcriptional and posttranscriptional regulators. ToxT is the transcription regulator that directly controls the production of the two major virulence factors, toxin-coregulated pilus (TCP) and cholera toxin (CT). The solved crystal structure of ToxT revealed an unstructured region in the N-terminal domain between residues 100 and 110. This region and the surrounding amino acids have been previously implicated in ToxT proteolysis, resistance to inhibition by negative effectors, and ToxT dimerization. To better characterize this region, site-directed mutagenesis was performed to assess the effects on ToxT proteolysis and bile sensitivity. This analysis identified specific mutations within this unstructured region that prevent ToxT proteolysis and other mutations that reduce inhibition by bile...
Journal of Bacteriology, Nov 24, 2014
Vibrio cholerae is the causative agent of the severe diarrheal disease cholera. The production of... more Vibrio cholerae is the causative agent of the severe diarrheal disease cholera. The production of the virulence factors that are required for human disease is controlled by a complex network of transcriptional and posttranscriptional regulators. ToxT is the transcription regulator that directly controls the production of the two major virulence factors, toxin-coregulated pilus (TCP) and cholera toxin (CT). The solved crystal structure of ToxT revealed an unstructured region in the N-terminal domain between residues 100 and 110. This region and the surrounding amino acids have been previously implicated in ToxT proteolysis, resistance to inhibition by negative effectors, and ToxT dimerization. To better characterize this region, site-directed mutagenesis was performed to assess the effects on ToxT proteolysis and bile sensitivity. This analysis identified specific mutations within this unstructured region that prevent ToxT proteolysis and other mutations that reduce inhibition by bile and unsaturated fatty acids. In addition, we found that mutations that affect the sensitivity of ToxT to bile also affect the sensitivity of ToxT to its positive effector, bicarbonate. These results suggest that a small unstructured region in the ToxT N-terminal domain is involved in multiple aspects of virulence gene regulation and response to human host signals.