title: DNA repair during bacterial competence? A potential role for the periplasmic ligase, Lig E

authors: Pan, Jolyn Tyn Tyn

abstract: The rapid rise in antibiotic resistance among pathogenic bacteria calls for better understanding of drivers of resistance and pathways by which it occurs. Identification of such mechanisms could identify novel pathways that can be targeted for therapeutic interventions. In particular, disruption of the DNA repair system, which includes ligases that seal breaks in DNA, would greatly discourage bacterial growth. Recently, an enigmatic ATP-dependent DNA ligase, Lig E, has been discovered in many species of antibiotic-resistant Gram-negative bacteria. This enzyme is not only minimal and compact, but also contains an N (amino)-terminal signal peptide that indicates a likely periplasmic location, as opposed to the cytoplasm, the location of genomic DNA. It is thus hypothesised that Lig E has a potential role in bacterial competence and aids in repairing breaks in damaged DNA obtained from the environment, a role which may enhance the acquisition of antibiotic resistance genes under DNA damaging conditions.
In recent years, there has been growing public concern about the human pathogen Neisseria gonorrhoeae, which causes the sexually transmitted disease, gonorrhoea. Previously easily treatable, this disease is now spreading at alarming rates due to the bacterium’s rapid acquisition of antibiotic resistance genes, attributable to its ability to take up pieces of DNA without regulation. It is in relation to this natural competence that Lig E is hypothesised to function, not only by accelerating the uptake process, but also by increasing the uptake efficiency. Thus, the aim of this thesis was to identify the cellular location and biological function of Lig E in N. gonorrhoeae (Ngo-Lig) by generating in vivo mutants, the effects of which were characterised both in vivo (growth experiment) and in vitro (ligation assays). Steps were also made towards developing an in vivo assay to test the role of Ngo-Lig in DNA uptake by optimisation of uptake reporter constructs.
Results obtained over the course of this thesis showed that disruption of Lig E in N. gonorrhoeae leads to a decrease in the rates of gonococcal growth. From this, the hypothesis of the role of Lig E evolved to also consider its potential role in biofilm formation, which is important for the bacterium’s attachment and infection.
Although further research into the biological role of Lig E are necessary, the results collected demonstrated potentially novel pathways involving Lig E that may be targeted by future drug developments to tackle this emerging threat in our community.

text: DNA repair during bacterial competence? A potential role for the periplasmic ligase, Lig E The rapid rise in antibiotic resistance among pathogenic bacteria calls for better understanding of drivers of resistance and pathways by which it occurs. Identification of such mechanisms could identify novel pathways that can be targeted for therapeutic interventions. In particular, disruption of the DNA repair system, which includes ligases that seal breaks in DNA, would greatly discourage bacterial growth. Recently, an enigmatic ATP-dependent DNA ligase, Lig E, has been discovered in many species of antibiotic-resistant Gram-negative bacteria. This enzyme is not only minimal and compact, but also contains an N (amino)-terminal signal peptide that indicates a likely periplasmic location, as opposed to the cytoplasm, the location of genomic DNA. It is thus hypothesised that Lig E has a potential role in bacterial competence and aids in repairing breaks in damaged DNA obtained from the environment, a role which may enhance the acquisition of antibiotic resistance genes under DNA damaging conditions.
In recent years, there has been growing public concern about the human pathogen Neisseria gonorrhoeae, which causes the sexually transmitted disease, gonorrhoea. Previously easily treatable, this disease is now spreading at alarming rates due to the bacterium’s rapid acquisition of antibiotic resistance genes, attributable to its ability to take up pieces of DNA without regulation. It is in relation to this natural competence that Lig E is hypothesised to function, not only by accelerating the uptake process, but also by increasing the uptake efficiency. Thus, the aim of this thesis was to identify the cellular location and biological function of Lig E in N. gonorrhoeae (Ngo-Lig) by generating in vivo mutants, the effects of which were characterised both in vivo (growth experiment) and in vitro (ligation assays). Steps were also made towards developing an in vivo assay to test the role of Ngo-Lig in DNA uptake by optimisation of uptake reporter constructs.
Results obtained over the course of this thesis showed that disruption of Lig E in N. gonorrhoeae leads to a decrease in the rates of gonococcal growth. From this, the hypothesis of the role of Lig E evolved to also consider its potential role in biofilm formation, which is important for the bacterium’s attachment and infection.
Although further research into the biological role of Lig E are necessary, the results collected demonstrated potentially novel pathways involving Lig E that may be targeted by future drug developments to tackle this emerging threat in our community.

year: 2021

title: Nonlocality and the critical Reynolds numbers of the minimum state magnetohydrodynamic turbulence

authors: Zhou, Ye

subjects: maths

abstract: Magnetohydrodynamic (MHD) systems can be strongly nonlinear (turbulent) when their kinetic and magnetic Reynolds numbers are high, as is the case in many astrophysical and space plasma flows. Unfortunately these high Reynolds numbers are typically much greater than those currently attainable in numerical simulations of MHD turbulence. A natural question to ask is how can researchers be sure that their simulations have reproduced all of the most influential physics of the flows and magnetic fields? In this paper, a metric is defined to indicate whether the necessary physics of interest has been captured. It is found that current computing resources will typically not be sufficient to achieve this minimum state metric.

text: Nonlocality and the critical Reynolds numbers of the minimum state magnetohydrodynamic turbulence Magnetohydrodynamic (MHD) systems can be strongly nonlinear (turbulent) when their kinetic and magnetic Reynolds numbers are high, as is the case in many astrophysical and space plasma flows. Unfortunately these high Reynolds numbers are typically much greater than those currently attainable in numerical simulations of MHD turbulence. A natural question to ask is how can researchers be sure that their simulations have reproduced all of the most influential physics of the flows and magnetic fields? In this paper, a metric is defined to indicate whether the necessary physics of interest has been captured. It is found that current computing resources will typically not be sufficient to achieve this minimum state metric.

year: 2011

title: Looking Past the Mess: Māori Homelessness and Mental Health Care

authors: Johnson, Diana

subjects: Homelessness

abstract: Homelessness is a pressing social and health concern that affects Māori disproportionately. This research explores the provision of mental health services to Māori who are homeless. The thesis has two primary aims. First, to document the experiences of Māori homeless people who live with mental health concerns and their relationships with mental health professionals. Second, to document the experiences of mental health professionals and how they interact with, provide care for, and build relationships with Māori Homeless. The skills of, and the difficulties faced by these professionals in provisions of quality of care are also considered. Three male and three female homeless participants were recruited from the Waikato and Auckland regions. All participants had received care from Non Governmental Organisations (NGOs) and/or District Health Board services (DHB). Participating mental health professionals included one female and five males. Mental health professionals included counsellors, therapists, psychologists, social workers, crisis team coordinator, and a cultural advisor. All participants took part in individual semi-structured interviews conducted in an open and conversational manner.  Key themes for homeless participants included their general life histories of mental illness, mental health service use, relationship with professionals, cultural issues, and concerns that Māori homeless wanted to discuss. Key themes for mental health professionals included their approaches when working with homeless people, relationship building, barriers to working with this group and possible solutions, linking with other professionals or organisations, and issues mental health professionals wanted to discuss. Findings highlight the importance of strong therapeutic relationships between homeless clients and mental health professionals, the need for more joined up (multi-level agency) approach to service delivery, and the importance of Māori ideology in restoring wellbeing and dignity. Findings suggest that the effectiveness of mental health service delivery relies in part on information provided by stakeholders. Information provided by homeless people and mental health professionals informs both service delivery and the ways in which practitioners can best support the needs of homeless people.

text: Looking Past the Mess: Māori Homelessness and Mental Health Care Homelessness is a pressing social and health concern that affects Māori disproportionately. This research explores the provision of mental health services to Māori who are homeless. The thesis has two primary aims. First, to document the experiences of Māori homeless people who live with mental health concerns and their relationships with mental health professionals. Second, to document the experiences of mental health professionals and how they interact with, provide care for, and build relationships with Māori Homeless. The skills of, and the difficulties faced by these professionals in provisions of quality of care are also considered. Three male and three female homeless participants were recruited from the Waikato and Auckland regions. All participants had received care from Non Governmental Organisations (NGOs) and/or District Health Board services (DHB). Participating mental health professionals included one female and five males. Mental health professionals included counsellors, therapists, psychologists, social workers, crisis team coordinator, and a cultural advisor. All participants took part in individual semi-structured interviews conducted in an open and conversational manner.  Key themes for homeless participants included their general life histories of mental illness, mental health service use, relationship with professionals, cultural issues, and concerns that Māori homeless wanted to discuss. Key themes for mental health professionals included their approaches when working with homeless people, relationship building, barriers to working with this group and possible solutions, linking with other professionals or organisations, and issues mental health professionals wanted to discuss. Findings highlight the importance of strong therapeutic relationships between homeless clients and mental health professionals, the need for more joined up (multi-level agency) approach to service delivery, and the importance of Māori ideology in restoring wellbeing and dignity. Findings suggest that the effectiveness of mental health service delivery relies in part on information provided by stakeholders. Information provided by homeless people and mental health professionals informs both service delivery and the ways in which practitioners can best support the needs of homeless people.

year: 2009