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: Lignin oxidation products in soil, dripwater and speleothems from four different sites in New Zealand

authors: Heidke, Inken

abstract: Lignin oxidation products (LOPs) are widely used as vegetation proxies in climate archives, such as sediment and peat cores. The total LOP concentration, Σ8, provides information on the abundance of vegetation, while the ratios C/V and S/V of the different LOP groups also provide information on the type of vegetation. Recently, LOP analysis has been successfully applied to speleothem archives. However, there are many open questions concerning the transport and microbial degradation of LOPs on their way from the soil into the cave system. These processes could potentially alter the original source-dependent LOP signals, in particular the C/V and S/V ratios, and thus complicate their interpretation in terms of past vegetation changes. We analyzed LOPs in leaf litter and different soil horizons as well as dripwater and flowstone samples from four different cave sites from different vegetation zones in New Zealand using ultrahigh-performance liquid chromatography coupled to high-resolution mass spectrometry. We test whether the original source-dependent LOP signal of the overlying vegetation is preserved and can be recovered from flowstone samples and investigate how the signal is altered by the transport from the soil to the cave. The LOP concentrations range from mg g−1 in the soil to ng g−1 in the flowstones. Our results demonstrate that, from the soil to the flowstone, the C/V and S/V ratios both increase, while the total lignin content, Σ8, strongly decreases. This shows that the LOP signal is strongly influenced by both transport and degradation processes. Nevertheless, the relative LOP signal from the overlying soil at the different cave sites is preserved in the flowstone. We emphasize that for the interpretation of C/V and S/V ratios in terms of past vegetation changes, it is important to compare only samples of the same type (e.g., speleothem, dripwater or soil) and to evaluate only relative variations.

text: Lignin oxidation products in soil, dripwater and speleothems from four different sites in New Zealand Lignin oxidation products (LOPs) are widely used as vegetation proxies in climate archives, such as sediment and peat cores. The total LOP concentration, Σ8, provides information on the abundance of vegetation, while the ratios C/V and S/V of the different LOP groups also provide information on the type of vegetation. Recently, LOP analysis has been successfully applied to speleothem archives. However, there are many open questions concerning the transport and microbial degradation of LOPs on their way from the soil into the cave system. These processes could potentially alter the original source-dependent LOP signals, in particular the C/V and S/V ratios, and thus complicate their interpretation in terms of past vegetation changes. We analyzed LOPs in leaf litter and different soil horizons as well as dripwater and flowstone samples from four different cave sites from different vegetation zones in New Zealand using ultrahigh-performance liquid chromatography coupled to high-resolution mass spectrometry. We test whether the original source-dependent LOP signal of the overlying vegetation is preserved and can be recovered from flowstone samples and investigate how the signal is altered by the transport from the soil to the cave. The LOP concentrations range from mg g−1 in the soil to ng g−1 in the flowstones. Our results demonstrate that, from the soil to the flowstone, the C/V and S/V ratios both increase, while the total lignin content, Σ8, strongly decreases. This shows that the LOP signal is strongly influenced by both transport and degradation processes. Nevertheless, the relative LOP signal from the overlying soil at the different cave sites is preserved in the flowstone. We emphasize that for the interpretation of C/V and S/V ratios in terms of past vegetation changes, it is important to compare only samples of the same type (e.g., speleothem, dripwater or soil) and to evaluate only relative variations.

year: 2021

title: Mokena Hou and his wife Rina

authors: Hart, Philip

abstract: Mokena Hou had a distinguished whakapapa, but as nephew to Hou was subordinate to the latter’s son, Karauna Hou. He was born near the Te Aroha hot pools, and his future wife, Rina, who also had illustrious ancestors, including some Ngati Haua, was born in the same area. Both were affiliated to several hapu. After the Hauraki tribes fled from Ngapuhi in 1821, he would be present at the battle of Taumatawiwi in 1830 (though he did not fight) and participated in a later siege of the Ngati Haua pa at Matamata. During the 1830s and later, he mostly cultivated land and dug gum in the lower Waihou region and as well as cultivating at Te Aroha. 
 After living at Kaitawa before the Thames goldfield opened, nearby, in 1867, he moved to Te Aroha, where he would live continuously, warding off the ambitions of Ngati Haua. When the land court investigated the ownership of blocks of land in Hauraki, he sought to obtain as many interests as possible, not always successfully, and tried to get more than his fair share of both land and revenue. 
A devoted Anglican, he assisted the early missionaries to the Waihou region. Wanting peaceful relations with Pakeha, he assisted both the surveying and the settlement of the Aroha Block. When gold was discovered at Te Aroha in 1880, he assisted the prospectors, opened his land for mining and for a township, and invested in some claims, expecting and obtaining a good financial reward. He may have assisted in making the hot pools a public reserve, and certainly gave sections of land within the settlement for public and religious purposes. When he and his wife died a month apart, they were fondly remembered.

text: Mokena Hou and his wife Rina Mokena Hou had a distinguished whakapapa, but as nephew to Hou was subordinate to the latter’s son, Karauna Hou. He was born near the Te Aroha hot pools, and his future wife, Rina, who also had illustrious ancestors, including some Ngati Haua, was born in the same area. Both were affiliated to several hapu. After the Hauraki tribes fled from Ngapuhi in 1821, he would be present at the battle of Taumatawiwi in 1830 (though he did not fight) and participated in a later siege of the Ngati Haua pa at Matamata. During the 1830s and later, he mostly cultivated land and dug gum in the lower Waihou region and as well as cultivating at Te Aroha. 
 After living at Kaitawa before the Thames goldfield opened, nearby, in 1867, he moved to Te Aroha, where he would live continuously, warding off the ambitions of Ngati Haua. When the land court investigated the ownership of blocks of land in Hauraki, he sought to obtain as many interests as possible, not always successfully, and tried to get more than his fair share of both land and revenue. 
A devoted Anglican, he assisted the early missionaries to the Waihou region. Wanting peaceful relations with Pakeha, he assisted both the surveying and the settlement of the Aroha Block. When gold was discovered at Te Aroha in 1880, he assisted the prospectors, opened his land for mining and for a township, and invested in some claims, expecting and obtaining a good financial reward. He may have assisted in making the hot pools a public reserve, and certainly gave sections of land within the settlement for public and religious purposes. When he and his wife died a month apart, they were fondly remembered.

year: 2016