Klaus Nüsslein | University of Massachusetts Amherst (original) (raw)

Papers by Klaus Nüsslein

Research paper thumbnail of Using Flow to Switch the Valency of Bacterial Capture on Engineered Surfaces Containing Immobilized Nanoparticles

Research paper thumbnail of Easy Come Easy Go: Surfaces Containing Immobilized Nanoparticles or Isolated Polycation Chains Facilitate Removal of Captured <i>Staphylococcus aureus</i> by Retarding Bacterial Bond Maturation

Research paper thumbnail of Antimicrobial surfaces containing cationic nanoparticles: How immobilized, clustered, and protruding cationic charge presentation affects killing activity and kinetics

Colloids and Surfaces B: Biointerfaces, 2015

Research paper thumbnail of Bacterial adhesion on hybrid cationic nanoparticle–polymer brush surfaces: Ionic strength tunes capture from monovalent to multivalent binding

Colloids and Surfaces B: Biointerfaces, Oct 1, 2011

Research paper thumbnail of Metagenomes from Eastern Brazilian Amazonian Floodplains in the Wet and Dry Seasons

Microbiology Resource Announcements

Here, we report the metagenomes from two Amazonian floodplain sediments in eastern Brazil. Tropic... more Here, we report the metagenomes from two Amazonian floodplain sediments in eastern Brazil. Tropical wetlands are well known for their role in the global carbon cycle. Microbial information on this diversified and dynamic landscape will provide further insights into its significance in regional and global biogeochemical cycles.

Research paper thumbnail of Maintaining grass coverage increases methane uptake in Amazonian pasture soils

Cattle ranching is the largest driver of deforestation in the Brazilian Amazon. The rainforest- t... more Cattle ranching is the largest driver of deforestation in the Brazilian Amazon. The rainforest- to-pasture conversion affects the methane cycle in upland soils, changing it from sink to source of atmospheric methane. However, it remains unknown if management practices could reduce the impact of land-use on methane cycling. In this work, we evaluated how pasture management can regulate the soil methane cycle either by maintaining continuous grass coverage on pasture soils, or by liming the soil to amend acidity. Methane fluxes from forest and pasture soils were evaluated in moisture-controlled greenhouse experiments with and without grass cover (Urochloa brizantha cv. Marandu) or liming. In parallel, we assessed changes in the soil microbial community structure of both bare pasture soil as well as rhizosphere soil through high throughput sequencing of the 16S rRNA gene, and quantified the methane cycling microbiota by their respective marker genes related to methane generation (mcrA)...

Research paper thumbnail of Maintaining grass coverage increases methane uptake in Amazonian pastures, with a reduction of methanogenic archaea in the rhizosphere

Science of The Total Environment

Research paper thumbnail of Increased soil moisture intensifies the impacts of forest-to-pasture conversion on methane emissions and methane-cycling communities in the Eastern Amazon

Environmental Research, 2022

Research paper thumbnail of Not just a methane source: Amazonian floodplain sediments harbour a high diversity of methanotrophs with different metabolic capabilities

Molecular Ecology, 2021

The Amazonian floodplain forests are dynamic ecosystems of great importance for the regional hydr... more The Amazonian floodplain forests are dynamic ecosystems of great importance for the regional hydrological and biogeochemical cycles and function as a significant CH4 source contributing to the global carbon balance. Unique geochemical factors may drive the microbial community composition and, consequently, affect CH4 emissions across floodplain areas. Here, we report the in situ composition of CH4 cycling microbial communities in Amazonian floodplain sediments. We considered how abiotic factors may affect the microbial community composition and, more specifically, CH4 cycling groups. We collected sediment samples during wet and dry seasons from three different types of floodplain forests, along with upland forest soil samples, from the Eastern Amazon, Brazil. We used high‐resolution sequencing of archaeal and bacterial 16S rRNA genes combined with real‐time PCR to quantify Archaea and Bacteria, as well as key functional genes indicative of the presence of methanogenic (mcrA) and met...

Research paper thumbnail of Seasonal dynamics of methane cycling microbial communities in Amazonian floodplain sediments

The Amazonian floodplain forests are dynamic ecosystems of great importance for the regional hydr... more The Amazonian floodplain forests are dynamic ecosystems of great importance for the regional hydrological and biogeochemical cycles and provide a significant contribution to the global carbon balance. Unique geochemical factors may drive the microbial community composition and, consequently, affect CH4emissions across floodplain areas. Here we provide the first report of thein situseasonal dynamics of CH4cycling microbial communities in Amazonian floodplains. We asked how abiotic factors may affect both overall and CH4cycling microbial communities and further investigated their responses to seasonal changes. We collected sediment samples during wet and dry seasons from three different types of floodplain forests, along with upland forest soil samples, from the Eastern Amazon, Brazil. We used high-resolution sequencing of archaeal and bacterial 16S rRNA genes combined with real-time PCR to quantify Archaea and Bacteria, as well as key functional genes indicative of the methanogenic (...

Research paper thumbnail of Rainforest-to-pasture conversion stimulates soil methanogenesis across the Brazilian Amazon

ABSTRACTThe Amazon rainforest is a biodiversity hotspot and large terrestrial carbon sink that is... more ABSTRACTThe Amazon rainforest is a biodiversity hotspot and large terrestrial carbon sink that is threatened by agricultural conversion. Rainforest-to-pasture conversion leads to the release of a potent greenhouse gas by converting soil from a methane sink into a source. The biotic methane cycle is driven by microorganisms; therefore, this study focused on active methane-cycling microorganisms and their functions across land-use types. We collected intact soil cores from three land use types (primary rainforest, pasture, and secondary rainforest) of two geographically distinct areas of the Brazilian Amazon (Santarém, Pará and Ariquemes, Rondônia) and performed DNA stable-isotope probing coupled with metagenomics to identify the active methanotrophs and methanogens. At both locations, we observed a significant change in the composition of the isotope-labeled methane-cycling microbial community across land use types, specifically an increase in the abundance and diversity of active me...

Research paper thumbnail of Belowground changes to community structure alter methane-cycling dynamics in Amazonia

ABSTRACTAmazonian rainforest is undergoing increasing rates of deforestation, driven primarily by... more ABSTRACTAmazonian rainforest is undergoing increasing rates of deforestation, driven primarily by cattle pasture expansion. Forest-to-pasture conversion has been associated with changes to ecosystem processes, including substantial increases in soil methane (CH4) emission. The drivers of this change in CH4flux are not well understood. To address this knowledge gap, we measured soil CH4flux, environmental conditions, and belowground microbial community attributes across a land use change gradient (old growth primary forest, cattle pasture, and secondary forest regrowth) in two Amazon Basin regions. Primary forest soils exhibited CH4uptake at modest rates, while pasture soils exhibited CH4emission at high but variable rates. Secondary forest soils exhibited low rates of CH4uptake, suggesting that forest regrowth following pasture abandonment could reverse the CH4sink-to-source trend. While few environmental variables were significantly associated with CH4flux, we identified numerous m...

Research paper thumbnail of New Biological Insights Into How Deforestation in Amazonia Affects Soil Microbial Communities Using Metagenomics and Metagenome-Assembled Genomes

Frontiers in microbiology, 2018

Deforestation in the Brazilian Amazon occurs at an alarming rate, which has broad effects on glob... more Deforestation in the Brazilian Amazon occurs at an alarming rate, which has broad effects on global greenhouse gas emissions, carbon storage, and biogeochemical cycles. In this study, soil metagenomes and metagenome-assembled genomes (MAGs) were analyzed for alterations to microbial community composition, functional groups, and putative physiology as it related to land-use change and tropical soil. A total of 28 MAGs were assembled encompassing 10 phyla, including both dominant and rare biosphere lineages. Amazon Acidobacteria subdivision 3, Melainabacteria, Microgenomates, and Parcubacteria were found exclusively in pasture soil samples, while Candidatus Rokubacteria was predominant in the adjacent rainforest soil. These shifts in relative abundance between land-use types were supported by the different putative physiologies and life strategies employed by the taxa. This research provides unique biological insights into candidate phyla in tropical soil and how deforestation may imp...

Research paper thumbnail of Differential Response of Acidobacteria Subgroups to Forest-to-Pasture Conversion and Their Biogeographic Patterns in the Western Brazilian Amazon

Frontiers in Microbiology, 2015

Research paper thumbnail of Surfaces for Competitive Selective Bacterial Capture from Protein Solutions

ACS Applied Materials & Interfaces, 2015

Research paper thumbnail of Land use, soil and litter chemistry drive bacterial community structures in samples of the rainforest and Cerrado (Brazilian Savannah) biomes in Southern Amazonia

European Journal of Soil Biology, 2015

Southern Amazonia harbors the largest agricultural frontier worldwide, where native vegetation ha... more Southern Amazonia harbors the largest agricultural frontier worldwide, where native vegetation has been converted to agriculture. Land use change in this region compromises deforestation as well as changes in agricultural management intensity (e.g. liming, fertilization, and number of crops) that shapes plant cover and soil chemistry. Our objective was to investigate the effects of these changes on soil bacterial community structure (i.e. community composition based on T-RFLP profiles of 16S rRNA and abundance of functional groups related to C and N cycling). Two representative agricultural regions within the biomes rainforest and Cerrado were chosen, each spanning land uses from native vegetation to pasture and soybean fields, and three replicated sites sampled for each land use type/region. Soil chemical alterations concurrent with land use changes to agriculture included increases in soil pH, Ca, Mg, P, K, and N concentrations, and easily decomposable litter. These alterations influenced bacterial community structure by changing both, community composition and functional gene abundance, findings supported by redundancy analysis and principal components analysis. Confirming one of our working hypotheses, based on the 16S rRNA gene, bacterial richness did not decrease from pristine vegetation to agricultural uses, but its composition shifted with land use change. In addition, a change in the abundance of microbial functional groups related to the production of the greenhouse gases N2O (denitrifiers, nosZ), and CH4 (methanogens, mcrA and methanotrophs, pmoA) reflected the influence of land use change in samples from both biomes. In accordance with our second hypothesis, the management intensive soybean soils exhibited the most distinct chemical (higher pH and nutrient levels) and microbiological profiles, including a significant decrease of the functional genes tested. In conclusion, our results identify land use intensity (namely its alterations in soil pH, C, litter degradability, pesticides and nutrient levels) as the driver for soil bacterial community structure (T-RFLP composition of 16S rRNA genes and functional gene abundance) in the studied samples. These formed a gradient of land use change consequences from native vegetation, to pasture and then to the soybean areas, which presented the most distinct chemical and bacterial profiles.

Research paper thumbnail of Conversion of the Amazon rainforest to agriculture results in biotic homogenization of soil bacterial communities

Proceedings of the National Academy of Sciences, 2012

The Amazon rainforest is the Earth’s largest reservoir of plant and animal diversity, and it has ... more The Amazon rainforest is the Earth’s largest reservoir of plant and animal diversity, and it has been subjected to especially high rates of land use change, primarily to cattle pasture. This conversion has had a strongly negative effect on biological diversity, reducing the number of plant and animal species and homogenizing communities. We report here that microbial biodiversity also responds strongly to conversion of the Amazon rainforest, but in a manner different from plants and animals. Local taxonomic and phylogenetic diversity of soil bacteria increases after conversion, but communities become more similar across space. This homogenization is driven by the loss of forest soil bacteria with restricted ranges (endemics) and results in a net loss of diversity. This study shows homogenization of microbial communities in response to human activities. Given that soil microbes represent the majority of biodiversity in terrestrial ecosystems and are intimately involved in ecosystem f...

Research paper thumbnail of Broad-spectrum antibacterial activity by a novel abiogenic peptide mimic

Microbiology, 2006

The human-mediated use and abuse of classical antibiotics has created a strong selective pressure... more The human-mediated use and abuse of classical antibiotics has created a strong selective pressure for the rapid evolution of antibiotic resistance. As resistance levels rise, and the efficacy of classical antibiotics wanes, the intensity of the search for alternative antimicrobials has increased. One class of molecules that has attracted much attention is the antimicrobial peptides (AMPs). They exhibit broad-spectrum activity, they are potent and they are widespread as part of the innate defence system of both vertebrates and invertebrates. However, peptides are complex molecules that suffer from proteolytic degradation. The ability to capture the essential properties of antimicrobial peptides in simple easy-to-prepare molecules that are abiotic in origin and non-proteolytic offers many advantages. Mechanistic and structural knowledge of existing AMPs was used to design a novel compound that mimics the biochemical activity of an AMP. This report describes the development and in vitr...

Research paper thumbnail of Antibacterial and Hemolytic Activities of Quaternary Pyridinium Functionalized Polynorbornenes

Macromolecular Chemistry and Physics, 2008

In this study, amphiphilic polyoxanorbornene with different quaternary alkyl pyridinium side chai... more In this study, amphiphilic polyoxanorbornene with different quaternary alkyl pyridinium side chains were synthesized. The biological efficiencies of these polymers, with various alkyl substituents, were determined by bacterial growth inhibition assays and hemolytic activity (HC50) against human red blood cells (RBCs) to provide selectivity of these polymers for bacterial over mammalian cells. A series of polymers with different alkyl substituents (ethyl, butyl, hexyl, octyl, decyl and phenylethyl) and two different molecular weights (3 and 10 kDa) were prepared. The impact of alkyl chain length divided the biological activity into two different cases: those with an alkyl substituent containing four or fewer carbons had a minimum inhibitory concentration (MIC) of 200 µg · mL−1 and a HC50 greater than 1 650 µg · mL−1, while those with six or more carbons had lower MICs ≤ 12.5 µg · mL−1 and HC50 ≤ 250 µg · mL−1. Using MSI‐78, the potent Magainin derivative which has an MIC = 12.0 µg · ...

Research paper thumbnail of Fast Disinfecting Antimicrobial Surfaces

Research paper thumbnail of Using Flow to Switch the Valency of Bacterial Capture on Engineered Surfaces Containing Immobilized Nanoparticles

Research paper thumbnail of Easy Come Easy Go: Surfaces Containing Immobilized Nanoparticles or Isolated Polycation Chains Facilitate Removal of Captured <i>Staphylococcus aureus</i> by Retarding Bacterial Bond Maturation

Research paper thumbnail of Antimicrobial surfaces containing cationic nanoparticles: How immobilized, clustered, and protruding cationic charge presentation affects killing activity and kinetics

Colloids and Surfaces B: Biointerfaces, 2015

Research paper thumbnail of Bacterial adhesion on hybrid cationic nanoparticle–polymer brush surfaces: Ionic strength tunes capture from monovalent to multivalent binding

Colloids and Surfaces B: Biointerfaces, Oct 1, 2011

Research paper thumbnail of Metagenomes from Eastern Brazilian Amazonian Floodplains in the Wet and Dry Seasons

Microbiology Resource Announcements

Here, we report the metagenomes from two Amazonian floodplain sediments in eastern Brazil. Tropic... more Here, we report the metagenomes from two Amazonian floodplain sediments in eastern Brazil. Tropical wetlands are well known for their role in the global carbon cycle. Microbial information on this diversified and dynamic landscape will provide further insights into its significance in regional and global biogeochemical cycles.

Research paper thumbnail of Maintaining grass coverage increases methane uptake in Amazonian pasture soils

Cattle ranching is the largest driver of deforestation in the Brazilian Amazon. The rainforest- t... more Cattle ranching is the largest driver of deforestation in the Brazilian Amazon. The rainforest- to-pasture conversion affects the methane cycle in upland soils, changing it from sink to source of atmospheric methane. However, it remains unknown if management practices could reduce the impact of land-use on methane cycling. In this work, we evaluated how pasture management can regulate the soil methane cycle either by maintaining continuous grass coverage on pasture soils, or by liming the soil to amend acidity. Methane fluxes from forest and pasture soils were evaluated in moisture-controlled greenhouse experiments with and without grass cover (Urochloa brizantha cv. Marandu) or liming. In parallel, we assessed changes in the soil microbial community structure of both bare pasture soil as well as rhizosphere soil through high throughput sequencing of the 16S rRNA gene, and quantified the methane cycling microbiota by their respective marker genes related to methane generation (mcrA)...

Research paper thumbnail of Maintaining grass coverage increases methane uptake in Amazonian pastures, with a reduction of methanogenic archaea in the rhizosphere

Science of The Total Environment

Research paper thumbnail of Increased soil moisture intensifies the impacts of forest-to-pasture conversion on methane emissions and methane-cycling communities in the Eastern Amazon

Environmental Research, 2022

Research paper thumbnail of Not just a methane source: Amazonian floodplain sediments harbour a high diversity of methanotrophs with different metabolic capabilities

Molecular Ecology, 2021

The Amazonian floodplain forests are dynamic ecosystems of great importance for the regional hydr... more The Amazonian floodplain forests are dynamic ecosystems of great importance for the regional hydrological and biogeochemical cycles and function as a significant CH4 source contributing to the global carbon balance. Unique geochemical factors may drive the microbial community composition and, consequently, affect CH4 emissions across floodplain areas. Here, we report the in situ composition of CH4 cycling microbial communities in Amazonian floodplain sediments. We considered how abiotic factors may affect the microbial community composition and, more specifically, CH4 cycling groups. We collected sediment samples during wet and dry seasons from three different types of floodplain forests, along with upland forest soil samples, from the Eastern Amazon, Brazil. We used high‐resolution sequencing of archaeal and bacterial 16S rRNA genes combined with real‐time PCR to quantify Archaea and Bacteria, as well as key functional genes indicative of the presence of methanogenic (mcrA) and met...

Research paper thumbnail of Seasonal dynamics of methane cycling microbial communities in Amazonian floodplain sediments

The Amazonian floodplain forests are dynamic ecosystems of great importance for the regional hydr... more The Amazonian floodplain forests are dynamic ecosystems of great importance for the regional hydrological and biogeochemical cycles and provide a significant contribution to the global carbon balance. Unique geochemical factors may drive the microbial community composition and, consequently, affect CH4emissions across floodplain areas. Here we provide the first report of thein situseasonal dynamics of CH4cycling microbial communities in Amazonian floodplains. We asked how abiotic factors may affect both overall and CH4cycling microbial communities and further investigated their responses to seasonal changes. We collected sediment samples during wet and dry seasons from three different types of floodplain forests, along with upland forest soil samples, from the Eastern Amazon, Brazil. We used high-resolution sequencing of archaeal and bacterial 16S rRNA genes combined with real-time PCR to quantify Archaea and Bacteria, as well as key functional genes indicative of the methanogenic (...

Research paper thumbnail of Rainforest-to-pasture conversion stimulates soil methanogenesis across the Brazilian Amazon

ABSTRACTThe Amazon rainforest is a biodiversity hotspot and large terrestrial carbon sink that is... more ABSTRACTThe Amazon rainforest is a biodiversity hotspot and large terrestrial carbon sink that is threatened by agricultural conversion. Rainforest-to-pasture conversion leads to the release of a potent greenhouse gas by converting soil from a methane sink into a source. The biotic methane cycle is driven by microorganisms; therefore, this study focused on active methane-cycling microorganisms and their functions across land-use types. We collected intact soil cores from three land use types (primary rainforest, pasture, and secondary rainforest) of two geographically distinct areas of the Brazilian Amazon (Santarém, Pará and Ariquemes, Rondônia) and performed DNA stable-isotope probing coupled with metagenomics to identify the active methanotrophs and methanogens. At both locations, we observed a significant change in the composition of the isotope-labeled methane-cycling microbial community across land use types, specifically an increase in the abundance and diversity of active me...

Research paper thumbnail of Belowground changes to community structure alter methane-cycling dynamics in Amazonia

ABSTRACTAmazonian rainforest is undergoing increasing rates of deforestation, driven primarily by... more ABSTRACTAmazonian rainforest is undergoing increasing rates of deforestation, driven primarily by cattle pasture expansion. Forest-to-pasture conversion has been associated with changes to ecosystem processes, including substantial increases in soil methane (CH4) emission. The drivers of this change in CH4flux are not well understood. To address this knowledge gap, we measured soil CH4flux, environmental conditions, and belowground microbial community attributes across a land use change gradient (old growth primary forest, cattle pasture, and secondary forest regrowth) in two Amazon Basin regions. Primary forest soils exhibited CH4uptake at modest rates, while pasture soils exhibited CH4emission at high but variable rates. Secondary forest soils exhibited low rates of CH4uptake, suggesting that forest regrowth following pasture abandonment could reverse the CH4sink-to-source trend. While few environmental variables were significantly associated with CH4flux, we identified numerous m...

Research paper thumbnail of New Biological Insights Into How Deforestation in Amazonia Affects Soil Microbial Communities Using Metagenomics and Metagenome-Assembled Genomes

Frontiers in microbiology, 2018

Deforestation in the Brazilian Amazon occurs at an alarming rate, which has broad effects on glob... more Deforestation in the Brazilian Amazon occurs at an alarming rate, which has broad effects on global greenhouse gas emissions, carbon storage, and biogeochemical cycles. In this study, soil metagenomes and metagenome-assembled genomes (MAGs) were analyzed for alterations to microbial community composition, functional groups, and putative physiology as it related to land-use change and tropical soil. A total of 28 MAGs were assembled encompassing 10 phyla, including both dominant and rare biosphere lineages. Amazon Acidobacteria subdivision 3, Melainabacteria, Microgenomates, and Parcubacteria were found exclusively in pasture soil samples, while Candidatus Rokubacteria was predominant in the adjacent rainforest soil. These shifts in relative abundance between land-use types were supported by the different putative physiologies and life strategies employed by the taxa. This research provides unique biological insights into candidate phyla in tropical soil and how deforestation may imp...

Research paper thumbnail of Differential Response of Acidobacteria Subgroups to Forest-to-Pasture Conversion and Their Biogeographic Patterns in the Western Brazilian Amazon

Frontiers in Microbiology, 2015

Research paper thumbnail of Surfaces for Competitive Selective Bacterial Capture from Protein Solutions

ACS Applied Materials & Interfaces, 2015

Research paper thumbnail of Land use, soil and litter chemistry drive bacterial community structures in samples of the rainforest and Cerrado (Brazilian Savannah) biomes in Southern Amazonia

European Journal of Soil Biology, 2015

Southern Amazonia harbors the largest agricultural frontier worldwide, where native vegetation ha... more Southern Amazonia harbors the largest agricultural frontier worldwide, where native vegetation has been converted to agriculture. Land use change in this region compromises deforestation as well as changes in agricultural management intensity (e.g. liming, fertilization, and number of crops) that shapes plant cover and soil chemistry. Our objective was to investigate the effects of these changes on soil bacterial community structure (i.e. community composition based on T-RFLP profiles of 16S rRNA and abundance of functional groups related to C and N cycling). Two representative agricultural regions within the biomes rainforest and Cerrado were chosen, each spanning land uses from native vegetation to pasture and soybean fields, and three replicated sites sampled for each land use type/region. Soil chemical alterations concurrent with land use changes to agriculture included increases in soil pH, Ca, Mg, P, K, and N concentrations, and easily decomposable litter. These alterations influenced bacterial community structure by changing both, community composition and functional gene abundance, findings supported by redundancy analysis and principal components analysis. Confirming one of our working hypotheses, based on the 16S rRNA gene, bacterial richness did not decrease from pristine vegetation to agricultural uses, but its composition shifted with land use change. In addition, a change in the abundance of microbial functional groups related to the production of the greenhouse gases N2O (denitrifiers, nosZ), and CH4 (methanogens, mcrA and methanotrophs, pmoA) reflected the influence of land use change in samples from both biomes. In accordance with our second hypothesis, the management intensive soybean soils exhibited the most distinct chemical (higher pH and nutrient levels) and microbiological profiles, including a significant decrease of the functional genes tested. In conclusion, our results identify land use intensity (namely its alterations in soil pH, C, litter degradability, pesticides and nutrient levels) as the driver for soil bacterial community structure (T-RFLP composition of 16S rRNA genes and functional gene abundance) in the studied samples. These formed a gradient of land use change consequences from native vegetation, to pasture and then to the soybean areas, which presented the most distinct chemical and bacterial profiles.

Research paper thumbnail of Conversion of the Amazon rainforest to agriculture results in biotic homogenization of soil bacterial communities

Proceedings of the National Academy of Sciences, 2012

The Amazon rainforest is the Earth’s largest reservoir of plant and animal diversity, and it has ... more The Amazon rainforest is the Earth’s largest reservoir of plant and animal diversity, and it has been subjected to especially high rates of land use change, primarily to cattle pasture. This conversion has had a strongly negative effect on biological diversity, reducing the number of plant and animal species and homogenizing communities. We report here that microbial biodiversity also responds strongly to conversion of the Amazon rainforest, but in a manner different from plants and animals. Local taxonomic and phylogenetic diversity of soil bacteria increases after conversion, but communities become more similar across space. This homogenization is driven by the loss of forest soil bacteria with restricted ranges (endemics) and results in a net loss of diversity. This study shows homogenization of microbial communities in response to human activities. Given that soil microbes represent the majority of biodiversity in terrestrial ecosystems and are intimately involved in ecosystem f...

Research paper thumbnail of Broad-spectrum antibacterial activity by a novel abiogenic peptide mimic

Microbiology, 2006

The human-mediated use and abuse of classical antibiotics has created a strong selective pressure... more The human-mediated use and abuse of classical antibiotics has created a strong selective pressure for the rapid evolution of antibiotic resistance. As resistance levels rise, and the efficacy of classical antibiotics wanes, the intensity of the search for alternative antimicrobials has increased. One class of molecules that has attracted much attention is the antimicrobial peptides (AMPs). They exhibit broad-spectrum activity, they are potent and they are widespread as part of the innate defence system of both vertebrates and invertebrates. However, peptides are complex molecules that suffer from proteolytic degradation. The ability to capture the essential properties of antimicrobial peptides in simple easy-to-prepare molecules that are abiotic in origin and non-proteolytic offers many advantages. Mechanistic and structural knowledge of existing AMPs was used to design a novel compound that mimics the biochemical activity of an AMP. This report describes the development and in vitr...

Research paper thumbnail of Antibacterial and Hemolytic Activities of Quaternary Pyridinium Functionalized Polynorbornenes

Macromolecular Chemistry and Physics, 2008

In this study, amphiphilic polyoxanorbornene with different quaternary alkyl pyridinium side chai... more In this study, amphiphilic polyoxanorbornene with different quaternary alkyl pyridinium side chains were synthesized. The biological efficiencies of these polymers, with various alkyl substituents, were determined by bacterial growth inhibition assays and hemolytic activity (HC50) against human red blood cells (RBCs) to provide selectivity of these polymers for bacterial over mammalian cells. A series of polymers with different alkyl substituents (ethyl, butyl, hexyl, octyl, decyl and phenylethyl) and two different molecular weights (3 and 10 kDa) were prepared. The impact of alkyl chain length divided the biological activity into two different cases: those with an alkyl substituent containing four or fewer carbons had a minimum inhibitory concentration (MIC) of 200 µg · mL−1 and a HC50 greater than 1 650 µg · mL−1, while those with six or more carbons had lower MICs ≤ 12.5 µg · mL−1 and HC50 ≤ 250 µg · mL−1. Using MSI‐78, the potent Magainin derivative which has an MIC = 12.0 µg · ...

Research paper thumbnail of Fast Disinfecting Antimicrobial Surfaces