Development in Aspergillus

AbstractThe genus Aspergillus represents a diverse group of fungi that are among the most abundant fungi in the world. Germination of a spore can lead to a vegetative mycelium that colonizes a substrate. The hyphae within the mycelium are highly heterogeneous with respect to gene expression, growth, and secretion. Aspergilli can reproduce both asexually and sexually. To this end, conidiophores and ascocarps are produced that form conidia and ascospores, respectively. This review describes the molecular mechanisms underlying growth and development of Aspergillus

Analysis of two distinct mycelial populations in liquid-grown Streptomyces cultures using a flow cytometry-based proteomics approach

Microbial Biotechnolog

Analysis of regulation of pentose utilisation in Aspergillus niger reveals evolutionary adaptations in Eurotiales

Aspergilli are commonly found in soil and on decaying plant material. D-xylose and L-arabinose are highly abundant components of plant biomass. They are released from polysaccharides by fungi using a set of extracellular enzymes and subsequently converted intracellularly through the pentose catabolic pathway (PCP)

Heterogeneity in Microbial Micro-colonies

Filamentous microbes play an important role in nutrient recycling by degrading dead organic material. Moreover, they can be used as cell factories for the production of pharmaceuticals and enzymes and metabolites. In my Thesis I studied the fungal cell factories Aspergillus niger and Aspergillus oryzae and bacterial cell factories of the genus Streptomyces. Filamentous microbes form colonies by means of an interconnected network of hyphae. Colonies formed in industrial bioreactors are ≤ 1mm and are dubbed micro-colonies. I studied whether all micro-colonies are the same or whether distinct populations of colonies can be distinguished. Statistical analysis following flowcytometry showed that liquid cultures of A. niger consisted of two populations of micro-colonies that differed in size and expression. It is known that micro-colony size depends on the surface properties of spores. Therefore I tested the ΔfwnA, ΔolvA and ΔbrnA strains that are affected in the biosynthesis of the pigment that resides at the surface of spores. These mutants formed larger and more homogenous micro-colonies than the control. Micro-colonies of ΔfwnA were even normally distributed. Additional analysis showed that conidia morphology and biophysical properties of the ΔbrnA and the ΔfwnA strains were similar as the control. However, conidia of ΔolvA were larger, more negatively charged, highly hydrophilic, and rodlets were almost completely absent. Two populations of micro-colonies could also be shown in liquid cultures of Streptomyces coelicolor, Streptomyces lividans, Streptomyces scabies, and Streptomyces griseus. Heterogeneity in A. niger is not only observed between micro-colonies but also within these colonies. The amount of RNA per individual hypha was 45 times higher at the periphery. Moreover, expression of genes was shown to be heterogeneous between neighboring hyphae. In A. oryzae it was shown that 40 % of the first three septa of hyphae at the periphery are closed. The plugging state of these septa did neither depend on the plugging state of neighboring septa nor on environmental conditions. Septa were always closed when a Woronin body was localized at the septal pore and were open when it was absent. This process is dynamic, implying that septal closure is reversible. Septal plugging explains hyphal heterogeneity between neighboring hyphae. Expression of glaA and aguA was normally distributed in neighboring hyphae of a strain lacking Woronin bodies, while it was heterogeneous in the wild-type background. The fact that microbial micro-colonies are heterogeneous has implications how analyses should be interpreted. By using the whole culture, an average is determined and may not reflect the composition or activity of individual populations. Therefore, individual populations should be studied to understand mechanisms underlying biological processe

Heterogeneous histopathology of cortical microbleeds in cerebral amyloid angiopathy

OBJECTIVE: To investigate the histopathologic substrate of microbleeds detected on 7T postmortem MRI in autopsy cases with severe cerebral amyloid angiopathy (CAA) and Alzheimer pathology. METHODS: Five decedents (mean age at death 79.6 +/- 5.7 years) with documented severe CAA and Alzheimer pathology on standard neuropathologic examination were selected from a local database. Formalin-fixed coronal brain slices were scanned at 7T MRI, including high-resolution T2- and T2*-weighted sequences. Representative microbleeds from each case were sampled for histopathologic analysis, including the presence of blood, blood breakdown products, and markers of ischemic tissue injury. RESULTS: On MRI, we identified >300 cortical and 4 subcortical microbleeds. Two out of 15 sampled cortical microbleeds corresponded histologically to erythrocytes (suggestive of recent hemorrhages), 4 to vasculopathies (fibrinoid necrosis in 3 and a cavernoma) without substantial parenchymal tissue injury, and 9 to accumulations of iron-positive siderophages without erythrocytes (suggestive of old hemorrhages) combined with mild to moderate degrees of chronic ischemic tissue injury. CONCLUSIONS: This study provides evidence for heterogeneous pathologic substrates and possibly different pathophysiologic mechanisms underlying MRI-observed cortical microbleeds in the context of advanced CAA and Alzheimer disease

Label-free fluorescence microscopy in fungi

Label-free fluorescence microscopy detects fluorescence originating from endogenous fluorophores, such as NAD(P)H, melanin and flavins. The emitted fluorescence (spectrum, lifetime and polarization) is characteristic for the molecule and its environment. In most cases, a specimen contains multiple autofluorescent molecules contributing to the overall fluorescence. Methods have been developed to break down the fluorescence into the contribution of its individual components. As a result, label-free microscopy can map biochemical properties of fluorophores spatially and over time at the level of the organism, tissue and cells. This is of interest for fungal cell biology and development. Moreover, it can be used in biotechnological applications to monitor the metabolic state within a bioreactor or to monitor the formation of secondary metabolites. Combining morphological and biochemical properties can also lead to new developments in fungal taxonomy, biomedical diagnostics, as well as the screening of fungal products such as mushrooms

Label-free fluorescence microscopy in fungi

Label-free fluorescence microscopy detects fluorescence originating from endogenous fluorophores, such as NAD(P)H, melanin and flavins. The emitted fluorescence (spectrum, lifetime and polarization) is characteristic for the molecule and its environment. In most cases, a specimen contains multiple autofluorescent molecules contributing to the overall fluorescence. Methods have been developed to break down the fluorescence into the contribution of its individual components. As a result, label-free microscopy can map biochemical properties of fluorophores spatially and over time at the level of the organism, tissue and cells. This is of interest for fungal cell biology and development. Moreover, it can be used in biotechnological applications to monitor the metabolic state within a bioreactor or to monitor the formation of secondary metabolites. Combining morphological and biochemical properties can also lead to new developments in fungal taxonomy, biomedical diagnostics, as well as the screening of fungal products such as mushrooms

Cortical microinfarcts detected in vivo on 3 Tesla MRI: clinical and radiological correlates

Item does not contain fulltextBACKGROUND AND PURPOSE: Cortical microinfarcts (CMIs) are a common postmortem finding associated with vascular risk factors, cognitive decline, and dementia. Recently, CMIs identified in vivo on 7 Tesla MRI also proved retraceable on 3 Tesla MRI. METHODS: We evaluated CMIs on 3 Tesla MRI in a population-based cohort of 194 nondemented older people (72-80 years) with systolic hypertension. Using a case-control design, participants with and without CMIs were compared on age, sex, cardiovascular risk factors, and white matter hyperintensity volume. RESULTS: We identified 23 CMIs in 12 participants (6%). CMIs were associated with older age, higher diastolic blood pressure, and a history of recent stroke. There was a trend for a higher white matter hyperintensity volume in participants with CMIs. CONCLUSIONS: We found an association of CMIs with clinical parameters, including age and cardiovascular risk factors. Although the prevalence of CMIs is relatively low, our results suggest that the study of CMIs in larger clinical studies is possible using 3 Tesla MRI. This opens the possibility of large-scale prospective investigation of the clinical relevance of CMIs in older people

Histopathology of Cerebral Microinfarcts and Microbleeds in Spontaneous Intracerebral Hemorrhage.

In patients with spontaneous intracerebral hemorrhage caused by different vasculopathies, cerebral microinfarcts have the same aspect on MRI and the same applies to cerebral microbleeds. It is unclear what pathological changes underlie these cerebral microinfarcts and cerebral microbleeds. In the current study, we explored the histopathological substrate of these lesions by investigating the brain tissue of 20 patients (median age at death 77 years) who died from ICH (9 lobar, 11 non-lobar) with a combination of post-mortem 7-T MRI and histopathological analysis. We identified 132 CMIs and 204 CMBs in 15 patients on MRI, with higher numbers of CMIs in lobar ICH patients and similar numbers of CMBs. On histopathology, CMIs and CMBs were in lobar ICH more often located in the superficial than in the deep layers of the cortex, and in non-lobar ICH more often in the deeper layers. We found a tendency towards more severe CAA scores in lobar ICH patients. Other histopathological characteristics were comparable between lobar and non-lobar ICH patients. Although CMIs and CMBs were found in different segments of the cortex in lobar ICH compared to non-lobar ICH patients, otherwise similar histopathological features of cortical CMIs and CMBs distant from the ICH suggest shared pathophysiological mechanisms in lobar and non-lobar ICH caused by different vasculopathies