Biology subjects

Vancova, M.

Publications and source records attributed to Vancova, M..

6 recordsLinked to original sources

bioRxiv2026

Crystalline guanine packed within vacuoles serves as nitrogen store in Chromera velia

Nitrogen is an important element for all living organisms. Photoautotrophic organisms need to assimilate nitrogen from the environment, therefore changes in nitrogen availability have a strong influence on their growth and metabolism. Many microalgae have been known to contain crystalline inclusions, and recently, it has been shown that many of these consist of purines like guanine and thus must be linked to the cellular nitrogen metabolisms. The alveolate alga Chromera velia contains such guanine crystals, and during its lifecycle, the alga is thought to be subjected to strong changes in external nitrogen availability. Here, we investigated the formation or decline of crystalline guanine in dependence of the availability of inorganic nitrogen in the growth medium. Cells were examined using polarised light microscopy, Raman micro-spectroscopy, chromatography (HPLC), transmission and scanning electron microscopy. The cellular guanine crystal content decreased during nitrogen starvation and increased upon transfer of the cells back to standard growth medium containing nitrate. Raman micro-spectroscopy showed that the crystals were composed of anhydrous guanine in beta-polytype. They appear in unspecific positions throughout the cell, and staining with the green dye Lysotracker DND-26 suggests that they are within vacuoles. Stacks of crystals could be observed in cells via freeze fracture and freeze etching electron microscopy, which unambiguously showed a membrane around the crystal aggregates, in a similar arrangement as has been shown for guanine storage vacuoles (GSV) in Chlamydomonas reinhardtii. We developed a method to isolate the guanine crystals from whole cells, and were able to obtain crystals which retained their flat, plate-like structure, matching the electron microscopic observations from whole cells. The isolated crystals were shown to consist of nitrogen rich compounds via energy-dispersive X-ray (EDX) analysis, and Raman micro-spectroscopy confirmed that they consist of guanine.

cell biology↗

bioRxiv2023

Concurrent infection of human brain with multiple species of Lyme disease spirochetes

Lyme disease (LD) spirochetes are well known to be able to disseminate into the tissues of infected hosts, including humans. The diverse strategies used by spirochetes to avoid the host immune system and persist in the host include active immune suppression, induction of immune tolerance, phase and antigenic variation, intracellular seclusion, and, importantly, incursion into immune privileged sites such as the brain. Invasion of immune privileged sites, like the brain allows the spirochetes not only escape from the host immune system but also can reduce the efficacy of antibiotic therapy. Here we present a case of the detection of DNA of spirochetes from Borrelia burgdorferi sensu lato complex from multiple loci of LD patients post-mortem brain. The presence of co-infection with Borrelia burgdorferi sensu stricto and Borrelia garinii in LD patients brain was confirmed by PCR. The presence of atypical spirochete morphology was confirmed by immunohistochemistry of the brain samples and also in tissues of experimental mice, infected with Borrelia by simultaneous injection of spirochetes subcutaneously and intraperitoneally. Even though both spirochete species were simultaneously present in brain, the brain regions where the two species were detected were different and non-overlapping.

microbiology↗

bioRxiv2022

Massive accumulation of strontium and barium in diplonemid protists

Barium (Ba) and strontium (Sr) are often used as proxies for the reconstruction of past marine productivity and global climate. The ability to accumulate Ba2+ and Sr2+ in the form of crystals is rare among eukaryotes. Here we report that unicellular heterotrophs called diplonemids (Euglenozoa), one of the most abundant groups of marine planktonic protists, accumulate conspicuous amounts of these trace elements in the form of intracellular barite (BaSO4) and celestite (SrSO4) crystals, in concentrations greater than in other known Ba/Sr-accumulating organisms. Moreover, these flagellates can uptake Sr2+ exclusively or together with Ba2+ and form (Ba,Sr)SO4. One species, Namystinia karyoxenos, is naturally capable of intracellular accumulation of Ba2+ and Sr2+ 42,000 and 10,000 times relative to the surrounding medium. Altering the amounts of both elements in the medium resulted in corresponding changes in the quantity and composition of crystals. Planktonic copepods fed with diplonemids produce celestite-rich fecal pellets, which facilitate deposition of these minerals on the seafloor. We propose that diplonemids, which emerged during the Neoproterozoic era, qualify as impactful players of Ba2+/Sr2+ cycling in the ocean that possibly contributed to sedimentary rock formation over long geological periods.

microbiology↗

bioRxiv2022

Minicollagens play the governing role in polar capsule formation in parasitic cnidarians, the Myxozoa

Minicollagens are major structural components in the biogenesis of nematocysts in Cnidaria. Sequence mining and recent proteomic analysis of polar capsules, homologues of cnidarian nematocysts, have confirmed the presence of minicollagens in this evolutionarily ancient cnidarian endoparasitic group. Nonetheless, the role of nematocyst-associated proteins in polar capsule morphogenesis has never been studied in myxozoans. Here, we report the gene expression of three myxozoan minicollagens, ncol-1, ncol-3, and the recently identified ncol-5, during the intrapiscine development of Myxidium lieberkuehni, the myxozoan parasite of Northern pike Esox lucius. Moreover, we determined the abundance and localisation of Ncol-1 and Ncol-5 proteins in the developing myxozoan stages by western blotting and by immunofluorescence and immunogold electron microscopy. We found that expression of minicollagens was spatiotemporally restricted to developing polar capsules in sporogonic stages. Intriguingly, Ncol-1 and Ncol-5 were localised as major components of the polar capsule wall and polar tubule. These results support the common origin of nematocysts and myxozoan polar capsules. Furthermore, our findings have practical implications for a more accurate identification of developmental stages of myxozoan parasites.

developmental biology↗

bioRxiv2021

Trypanosome morphogenesis involves recruitment of a pleckstrin homology domain protein by an orphan kinesin to the microtubule quartet

Kinesins are motor proteins found in all eukaryotic lineages that move along microtubules to mediate cellular processes such as mitosis and intracellular transport. In trypanosomatids, the kinesin superfamily has undergone a prominent expansion, resulting in one of the most diverse kinesin repertoires that includes the two kinetoplastid-restricted families X1 and X2. Here, we characterize in Trypanosoma brucei TbKifX2A, an orphaned X2 kinesin. TbKifX2A tightly interacts with TbPH1, a kinesin-like protein with a likely inactive motor domain, a rarely reported occurrence. Both TbKifX2A and TbPH1 localize to the microtubule quartet (MtQ), a characteristic but poorly understood cytoskeletal structure that wraps around the flagellar pocket as it extends to the cell body anterior. The proximal proteome of TbPH1 revealed two other interacting proteins, the flagellar pocket protein FP45 and intriguingly another X2 kinesin, TbKifX2C. Simultaneous ablation of TbKifX2A/TbPH1 results in the depletion of FP45 and TbKifX2C and also an expansion of the flagellar pocket, among other morphological defects. TbKifX2A is the first motor protein to be localized to the MtQ. The observation that TbKifX2C also associates with the MtQ suggests that the X2 kinesin family may have co-evolved with the MtQ, both kinetoplastid-specific traits.

molecular biology↗

bioRxiv2021

Selective and reversible disruption of mitochondrial inner membrane protein complexes by lipophilic cations

Triphenylphosphonium (TPP) derivatives are commonly used to target chemical into mitochondria. We show that alkyl-TPP cause reversible, dose- and hydrophobicity-dependent alterations of mitochondrial morphology and function and a selective decrease of mitochondrial inner membrane proteins including subunits of the respiratory chain complexes, as well as components of the mitochondrial calcium uniporter complex. The treatment with alkyl-TPP resulted in the cleavage of the pro-fusion and cristae organisation regulator Optic atrophy-1. The structural and functional effects of alkyl-TPP were found to be reversible and not merely due to loss of membrane potential. A similar effect was observed with the mitochondria-targeted antioxidant MitoQ.

biochemistry↗