Biology subjects

Panzera, A.

Publications and source records attributed to Panzera, A..

3 recordsLinked to original sources

bioRxiv2025

DNA Wrapping by a Tetrameric Bacterial Histone

Histones are conserved DNA-packaging proteins found across all domains of life. In eukaryotes, canonical histones form octamers that wrap [~]147 base pairs of DNA into nucleosomes -- the fundamental units of chromatin. In archaea, histones form dimers that further multimerize into extended hypernucleosomes along DNA. Although bacteria were long thought to lack histones, recent studies have uncovered histone homologs in diverse bacterial lineages, many of which possess key DNA-binding features. We previously characterized HBb, a bacterial histone from Bdellovibrio bacteriovorus, which binds DNA as a dimer and induces bending. Here, we describe HLp from Leptospira perolatii, a representative of a distinct bacterial histone group. Crystallographic and biophysical analyses reveal that HLp forms stable tetramers. Like HBb, HLp binds DNA non-specifically; however, it adopts a different mode of interaction -- wrapping [~]60 base pairs of DNA around its tetrameric core. This wrapping mode, supported by molecular dynamics simulations and DNA-binding assays, promotes DNA compaction and alters its topology. When expressed heterologously in Escherichia coli, HLp reorganizes nucleoid morphology, consistent with a role in chromatin organization. These findings expand the known repertoire of histone-DNA interaction in bacteria and underscore the structural and functional diversity of histone-based genome organization across the tree of life.

biochemistry↗

bioRxiv2022

The targeted deletion of genes responsible for expression of the Mth60 fimbriae leads to loss of cell-cell connections in M. thermautotrophicus ΔH

This study was continued by the Environmental Biotechnology Group of the University of Tubingen in memoriam to Reinhard Wirth, who initiated the work on Mth60 fimbriae at the University of Regensburg. Growth in biofilms or biofilm-like structures is the prevailing lifestyle for most microbes in nature. The first step to initiate biofilms is the adherence of microbes to biotic and abiotic surfaces. Therefore, it is important to elucidate the initial step of biofilm formation, which is generally established through cell-surface structures (i.e., cell appendages), such as fimbriae or pili, that adhere to surfaces. The Mth60 fimbriae of Methanothermobacter thermautotrophicus {Delta}H are one of only few known archaeal cell appendages that do not assemble via the type-IV assembly mechanism. Here, we report the constitutive expression of Mth60 fimbriae-encoding genes from a shuttle-vector construct, as well as the deletion of the Mth60 fimbriae-encoding genes from the genomic DNA of M. thermautotrophicus {Delta}H. We expanded our system for genetic modification of M. thermautotrophicus {Delta}H by an allelic-exchange method. While overexpression of the respective genes resulted in an increase of the Mth60 fimbriae, deletion of the Mth60 fimbriae-encoding genes led to a loss of Mth60 fimbriae in planktonic cells of M. thermautotrophicus {Delta}H. This either increased or decreased number of Mth60 fimbriae correlated with a significant increase or decrease of biotic cell-cell connections in the respective M. thermautotrophicus {Delta}H strains compared to the wild-type strain. Originality-Significance StatementMethanothermobacter spp. have been studied for the biochemistry of hydrogenotrophic methanogenesis for many years. However, due to the lack of genetic tools, the detailed investigation of certain aspects, such as regulatory processes, was not possible. Here, we amend our genetic toolbox for M. thermautotrophicus {Delta}H with an allelic exchange method. We report the deletion of genes that encode for the Mth60 fimbriae. Our findings provide a first insight into the regulation of the expression of these genes and reveal a role of the Mth60 fimbriae in the formation of cell-cell connections of M. thermautotrophicus {Delta}H.

microbiology↗

bioRxiv2017

Ciliomotor circuitry underlying whole-body coordination of ciliary activity in the Platynereis larva

Ciliated surfaces harbouring synchronously beating cilia can generate fluid flow or drive locomotion. In ciliary swimmers, ciliary beating, arrests, and changes in beat frequency are often coordinated across extended or discontinuous surfaces. To understand how such coordination is achieved, we studied the ciliated larvae of Platynereis dumerilii, a marine annelid. Platynereis larvae have segmental multiciliated cells that regularly display spontaneous coordinated ciliary arrests. We used whole-body connectomics, activity imaging, transgenesis, and neuron ablation to characterize the ciliomotor circuitry. We identified cholinergic, serotonergic, and catecholaminergic ciliomotor neurons. The synchronous rhythmic activation of cholinergic cells drives the coordinated arrests of all cilia. The serotonergic cells are active when cilia are beating. Serotonin inhibits the cholinergic rhythm, and increases ciliary beat frequency. Based on their connectivity and alternating activity, the catecholaminergic cells may generate the rhythm. The ciliomotor circuitry thus constitutes a stop-and-go pacemaker system for the whole-body coordination of ciliary locomotion.

neuroscience↗