Biology subjects

Recalde, A.

Publications and source records attributed to Recalde, A..

5 recordsLinked to original sources

bioRxiv2026

Region-specific patterns of sexual shape variation in the human bony labyrinth: 3D geometric morphometric analysis of a sample with known genomic sex

The human bony labyrinth has attracted increasing interest because of its taxonomic, evolutionary, and functional significance. Although sexual dimorphism has been reported in several aspects of the temporal bone, the extent to which sex, age, size, and allometry contribute to labyrinth shape variation remains poorly understood. Here, we investigated patterns of sexual shape variation in the human bony labyrinth using three-dimensional geometric morphometrics in a sample of 98 archaeological individuals from South America with known genomic sex. Centroid size and allometric effects were assessed in a subset of 90 individuals with comparable metric scaling. In addition to analysing the complete labyrinth, the cochlea and semicircular canals were examined separately to evaluate region-specific patterns of sexual shape variation. Principal Component Analysis showed extensive overlap between females and males, and overall labyrinth shape did not differ significantly between sexes. Males exhibited significantly larger labyrinths than females, and centroid size explained a small but significant proportion of overall shape variation. Regional analyses showed no evidence of significant sexual shape differences in the cochlea or in any individual semicircular canal when analysed separately. In contrast, the combined semicircular canal system exhibited subtle but significant sexual shape variation independent of centroid size, whereas morphological disparity did not differ between sexes. The geometric comparison of the female and male consensus configurations further showed that sexual shape variation was regionally heterogeneous. Whereas the cochlea exhibited a pattern of localized changes with low directional coherence, the semicircular canals displayed more coordinated regional shape changes. The male consensus also exhibited slightly higher canal circularity across all three semicircular canals, particularly the posterior canal, while differences in canal-plane orientation remained minimal. These findings demonstrate that sexual shape variation in the human bony labyrinth is subtle and anatomically partitioned among its components. Although significant sex differences in centroid size were detected across most anatomical regions, overall labyrinth shape and cochlear morphology were primarily influenced by allometry, whereas significant sex-related shape differences were detected only when the semicircular canals were considered as an integrated anatomical system. These findings demonstrate that sexual dimorphism in the human bony labyrinth is subtle but regionally heterogeneous, with the cochlea and semicircular canals exhibiting distinct patterns of shape variation, suggesting that these structures are influenced by different developmental, functional, and evolutionary processes.

evolutionary biology↗

bioRxiv2024

New components of the community based DNA-repair mechanism in Sulfolobales

After exposure to UV light, Sulfolobus acidocaldarius cells aggregate in a species-specific manner to exchange DNA and repair double-strand breaks via homologous recombination. The formation of cell-cell interactions is mediated by Ups pili. DNA exchange subsequently occurs through the Ced system, which imports DNA. To identify novel players in these processes, we investigated several genes upregulated after UV exposure by creating in-frame deletion mutants and performing cell aggregation and DNA exchange assays. This led to the identification of two novel components involved in the Ups and Ced systems: UpsC, a minor pilin of the Ups pili, and CedD, a VirD4-like ATPase essential for DNA import. Altogether, these findings provide new insights into the fascinating DNA damage response of Sulfolobales.

microbiology↗

bioRxiv2024

The use of thermostable fluorescent proteins for live imaging in Sulfolobus acidocaldarius

Among hyperthermophilic organisms, in vivo protein localization is challenging due to the high growth temperatures that can disrupt proper folding and function of mostly mesophilic-derived fluorescent proteins. While protein localization in the thermophilic model archaeon S. acidocaldarius has been achieved using antibodies with fluorescent probes in fixed cells, the use of thermostable fluorescent proteins in thermophilic archaea has so far been unsuccessful. Given the significance of live protein localization in the field of archaeal cell biology, we aimed to identify fluorescent proteins for use in S. acidocaldarius. To achieve this, we expressed various previously published and optimized thermostable fluorescent proteins along with fusion proteins of interest and analyzed the cells using flow cytometry and (thermo-) fluorescent microscopy. Of the tested proteins, Thermal Green Protein (TGP) exhibited the brightest fluorescence when expressed in Sulfolobus cells. By optimizing the linker between TGP and a protein of interest, we could additionally successfully fuse proteins with minimal loss of fluorescence. TGP-CdvB and TGP-PCNA1 fusions displayed localization patterns consistent with previous immunolocalization experiments. These initial results in protein localization in S. acidocaldarius at high temperatures, combined with recent advancements in thermomicroscopy, open new avenues in the field of archaeal cell biology. This progress finally enables localization experiments in thermophilic archaea, which have so far been limited to mesophilic organisms.

microbiology↗

bioRxiv2024

Role of VapBC4 toxin-antitoxin system of Sulfolobus acidocaldarius in heat stress adaptation

Toxin-antitoxin (TA) systems are important for stress adaptation in prokaryotes, including persistence, antibiotic resistance, pathogenicity, and biofilm formation. Toxins can cause cell death, reversible growth stasis, and direct inhibition of crucial cellular processes through various mechanisms, while antitoxins neutralize the effects of toxins. In bacteria, these systems have been studied in detail, whereas their function in archaea remains elusive. During heat stress, the thermoacidophilic archaeon Sulfolobus acidocaldarius exhibited an increase in the expression of several bicistronic type II vapBC TA systems, with the highest expression observed in the vapBC4 system. In the current study, we performed a comprehensive biochemical characterization of the VapBC4 TA system, establishing it as a bonafide type II toxin-antitoxin system. The VapC4 toxin is shown to have high-temperature catalyzed RNase activity specific for mRNA and rRNA, while the VapB4 antitoxin inhibits the toxic activity of VapC4 by interacting with it. VapC4 toxin expression led to heat-induced persister-like cell formation, allowing the cell to cope with the stress. Furthermore, this study explored the impact of vapBC4 deletion on biofilm formation, whereby deletion of vapC4 led to increased biofilm formation, suggesting its role in regulating biofilm formation. Thus, during heat stress, the liberated VapC4 toxin in cells could potentially signal a preference for persister cell formation over biofilm growth. Thus, our findings shed light on the diverse roles of the VapC4 toxin in inhibiting translation, inducing persister cell formation, and regulating biofilm formation in S. acidocaldarius, enhancing our understanding of TA systems in archaea. IMPORTANCEThis research enhances our knowledge of Toxin-antitoxin (TA) systems in archaea, specifically in the thermoacidophilic archaeon Sulfolobus acidocaldarius. TA systems are widespread in both bacterial and archaeal genomes, indicating their evolutionary importance. However, their exact functions in archaeal cellular physiology are still not well understood. This study sheds light on the complex roles of TA systems and their critical involvement in archaeal stress adaptation, including persistence and biofilm formation. By focusing on S. acidocaldarius, which lives in habitats with fluctuating temperatures that can reach up to 90, the study reveals the unique challenges and survival mechanisms of this organism. The detailed biochemical analysis of the VapBC4 TA system, and its crucial role during heat stress, provides insights into how extremophiles can survive in harsh conditions. The findings of this study show the various functions of the VapC4 toxin, including inhibiting translation, inducing persister-like cell formation, and regulating biofilm formation. This knowledge improves our understanding of TA systems in thermoacidophiles and has broader implications for understanding how microorganisms adapt to extreme environments.

microbiology↗

bioRxiv2024

Glycerol degradation in the thermoacidophilic crenarchaeon Sulfolobus acidocaldarius involves an unusual glycerol-3-phosphate dehydrogenase

Glycerol is highly abundant in nature and serve as carbon source for many organisms. Also, several Archaea have the genetic capacity to grow on glycerol but its degradation has so far only been studied Haloferax volcanii. Herein, the thermoacidophilic crenarchaeon Sulfolobus acidocaldarius was shown to grow with glycerol as sole carbon and energy source. After uptake likely involving facilitated diffusion, glycerol is degraded via phosphorylation to glycerol-3-phosphate followed by oxidation to dihydroxyacetone phosphate (DHAP) catalyzed by glycerol kinase (GK) by an unusual quinone reducing FAD-dependent glycerol-3-phosphate dehydrogenase (G3PDH), respectively. The S. acidocaldarius genome harbors two paralogous copies of each GK and G3PDH. However, only one of these GK-G3PDH couples (Saci_2031-2033) is highly upregulated on glycerol. Deletion of the saci_2033 gene encoding GK abolished growth on glycerol and GK activity in crude extracts. In contrast, deletion of the second GK gene (saci_1117) had only minor effects indicating that only one of the two GK-G3PDH couples is essential. Biochemical characterization revealed that both isoenzymes of each, GK and G3PDH, were functionally similar. Whereas the GKs showed high similarity to known enzymes from Bacteria and Eukaryotes, the G3PDHs represent unusual homologues of the bacterial GlpA subunit of the GlpABC complex with remarkable C-terminal sequence differences and a novel type of membrane anchoring via a CoxG-like protein (Saci_2031). Further sequence analyzes discovered a higher versatility of G3PDHs in Archaea with respect to interacting proteins, electron transfer, and membrane anchoring likely reflecting tailored evolutionary solutions to meet different requirements caused by life styles and electron acceptors.

microbiology↗