Biology subjects

Matysik, A.

Publications and source records attributed to Matysik, A..

3 recordsLinked to original sources

bioRxiv2018

Apparent oxygen half saturation constant for nitrifiers: genus specific, inherent physiological property, or artefact of colony morphology?

We report that a single Nitrospira sublineage I OTU performs nitrite oxidation in several full-scale domestic wastewater treatment plants (WWTPs) in the tropics (29-31 {degrees}C). Contrary to the prevailing theory for the relationship between nitrite oxidizing bacteria (NOB) and ammonia oxidizing bacteria (AOB), members of the Nitrospira sublineage I OTU had an apparent half saturation coefficient, Ks(app) lower than that of the full-scale domestic activated sludge cohabitant AOB (0.09 {+/-} 0.02 g O2 m-3 versus 0.3 {+/-} 0.03 g O2 m-3). Paradoxically, NOB may thus thrive under conditions of low oxygen supply. Low dissolved oxygen (DO) conditions could enrich for and high aeration inhibit the NOB in a long-term lab-scale reactor. The relative abundance of Nitrospira gradually decreased with increasing DO until it was washed out. Nitritation was sustained even after the DO was lowered subsequently. Based on 3D-fluorescence in situ hybridization (FISH) image analysis, the morphologies of AOB and NOB microcolonies responded to DO levels in accordance with their apparent oxygen half saturation constant Ks(app). When exposed to the same oxygenation level, NOB formed densely packed spherical clusters with a low surface area-to-volume ratio compared to the Nitrosomonas-like AOB clusters, which maintained a porous and non-spherical morphology. Microcolony morphology is thus a way for AOB and NOB to regulate oxygen exposure and sustain the mutualistic interaction. However, short-term high DO exposure can select for AOB and against NOB in full-scale domestic WWTPs and such population dynamics depend on which specific AOB and NOB species predominate under given environmental conditions.

systems biology↗

bioRxiv2017

Extracellular Electron Transfer Powers Enterococcus faecalis Biofilm Metabolism

Enterococci are important human commensals and significant opportunistic pathogens associated with endocarditis, urinary tract infections, wound and surgical site infections, and medical device associated infections. These infections often become chronic upon the formation of biofilm. The biofilm matrix establishes properties that distinguish this state from free-living bacterial cells and increase tolerance to antimicrobial interventions. The metabolic versatility of the Enterococci is reflected in the diversity and complexity of environments and communities in which they thrive. Understanding metabolic factors governing colonization and persistence in different host niches can reveal factors influencing the transition from commensal to opportunistic pathogen. Here, we report a new form of iron-dependent metabolism for Enterococcus faecalis where, in the absence of heme, respiration components can be utilised for extracellular electron transfer (EET). Iron augments E. faecalis biofilm growth and generates alterations in biofilm matrix, cell spatial distribution, and biofilm matrix properties. We identify the genes involved in iron-augmented biofilm growth and show that it occurs by promoting EET to iron within biofilm.\n\nSignificanceBacterial metabolic versatility is often key in dictating the outcome of host-pathogen interactions, yet determinants of metabolic shifts are difficult to resolve. The bacterial biofilm matrix provides the structural and functional support that distinguishes this state from free-living bacterial cells. Here, we show that the biofilm matrix provides access to resources necessary for metabolism and growth which are otherwise inaccessible in the planktonic state. Our data shows that in the absence of heme, components of Enterococcus faecalis respiration (l-lactate dehydrogenase and acetaldehyde dehydrogenase) may function as initiators of EET through the cytoplasmic membrane quinone pool and utilize matrix-associated iron to carry out EET. The presence of iron resources within the biofilm matrix leads to enhanced biofilm growth.

microbiology↗

bioRxiv2016

Drosophila BEACH domain autophagic adaptor blue cheese shuttles between vesicle populations and is required for an early step in autophagy

Drosophila melanogaster blue cheese (bchs) encodes a large BEACH (Beige and Chediak-Higashi) family protein that is postulated to function as an adaptor protein with roles in vesicle trafficking. Mutation in bchs leads to the accumulation of ubiquitinated aggregates in aged brains, presumably because of a conserved function with its human homologue Autophagy-Linked FYVE (ALFY), which interacts with Atg5 and p62 to promote the clearance of aggregate-prone proteins. In this study, we present pharmacological and genetic evidence using a well-defined larval motorneuron paradigm that in Drosophila bchs mutants, autophagic deficit contributes to neurodegeneration. Specifically, we show that motorneuron death in larvae is accompanied by the accumulation of prominent ubiquitinated aggregates in synaptic termini, and that these are sensitive to autophagy modulating drugs. In primary bchs neurons, early autophagic compartments increase in number and intensity based on Atg5 expression, but fail to progress to Atg8-labelled compartments, indicating non-clearance. A rescuing transgene encoding the longest Bchs BEACH domain isoform not only reverses this defect, but also greatly increases Atg8 compartment number and rescues neuronal death. Although only a small fraction of Bchs colocalizes with these markers under wild-type conditions, the population of Bchs that does associate with autophagosomes shuttles between different locations depending on how autophagy is induced. These observations, together with epistatic relationships between bchs mutant alleles and autophagy-modulating drugs and genetic backgrounds, points to a model whereby BEACH domain isoforms of Bchs participate in the early steps of autophagy by recruiting Atg5 to target substrates for clearance, and that Bchs association with different parts of the autophagy machinery depends upon the type of autophagic stress imposed upon the neuron.

cell biology↗