1,214 research outputs found
Voluntary standards and the SDGs: Mapping public-private complementarities for sustainable development
Characterization and evolution of cell division and cell wall synthesis genes in the bacterial phyla Verrucomicrobia, Lentisphaerae, Chlamydiae and Planctomycetes and phylogenetic comparison with rRNA genes
In the past, studies on the relationships of the bacterial phyla Planctomycetes, Chlamydiae, Lentisphaerae, and
Verrucomicrobia using different phylogenetic markers have been controversial. Investigations based on 16S
rRNA sequence analyses suggested a relationship of the four phyla, showing the branching order Planctomycetes,
Chlamydiae, Verrucomicrobia/Lentisphaerae. Phylogenetic analyses of 23S rRNA genes in this study also
support a monophyletic grouping and their branching orderāthis grouping is significant for understanding
cell division, since the major bacterial cell division protein FtsZ is absent from members of two of the phyla
Chlamydiae and Planctomycetes. In Verrucomicrobia, knowledge about cell division is mainly restricted to the
recent report of ftsZ in the closely related genera Prosthecobacter and Verrucomicrobium. In this study, genes of
the conserved division and cell wall (dcw) cluster (ddl, ftsQ, ftsA, and ftsZ) were characterized in all verrucomicrobial
subdivisions (1 to 4) with cultivable representatives (1 to 4). Sequence analyses and transcriptional
analyses in Verrucomicrobia and genome data analyses in Lentisphaerae suggested that cell division is based on
FtsZ in all verrucomicrobial subdivisions and possibly also in the sister phylum Lentisphaerae. Comprehensive
sequence analyses of available genome data for representatives of Verrucomicrobia, Lentisphaerae, Chlamydiae,
and Planctomycetes strongly indicate that their last common ancestor possessed a conserved, ancestral type of
dcw gene cluster and an FtsZ-based cell division mechanism. This implies that Planctomycetes and Chlamydiae
may have shifted independently to a non-FtsZ-based cell division mechanism after their separate branchings
from their last common ancestor with Verrucomicrobia
Characterization of bacterial operons consisting of two tubulins and a kinesin-like gene by the novel Two-Step Gene Walking method
Tubulins are still considered as typical proteins of
Eukaryotes. However, more recently they have been
found in the unusual bacteria Prosthecobacter
(btubAB). In this study, the genomic organization
of the btub-genes and their genomic environment
were characterized by using the newly developed
Two-Step Gene Walking method. In all investigated
Prosthecobacters, btubAB are organized in a typical
bacterial operon. Strikingly, all btub-operons
comprise a third gene with similarities to kinesin
light chain sequences. The genomic environments
of the characterized btub-operons are always
different. This supports the hypothesis that this
group of genes represents an independent functional
unit, which was acquired by Prosthecobacter
via horizontal gene transfer. The newly developed
Two-Step Gene Walking method is based on
randomly primed polymerase chain reaction (PCR).
It presents a simple workflow, which comprises only
two major stepsāa Walking-PCR with a single
specific outward pointing primer (step 1) and the
direct sequencing of its product using a nested
specific primer (step 2). Two-Step Gene Walking
proved to be highly efficient and was successfully
used to characterize over 20 kb of sequence not only
in pure culture but even in complex non-pure culture
samples
Protein secretion and surface display in Gram-positive bacteria
The cell wall peptidoglycan of Gram-positive bacteria functions as a surface organelle for the transport and assembly of proteins that interact with the environment, in particular, the tissues of an infected host. Signal peptide-bearing precursor proteins are secreted across the plasma membrane of Gram-positive bacteria. Some precursors carry C-terminal sorting signals with unique sequence motifs that are cleaved by sortase enzymes and linked to the cell wall peptidoglycan of vegetative forms or spores. The sorting signals of pilin precursors are cleaved by pilus-specific sortases, which generate covalent bonds between proteins leading to the assembly of fimbrial structures. Other precursors harbour surface (S)-layer homology domains (SLH), which fold into a three-pronged spindle structure and bind secondary cell wall polysaccharides, thereby associating with the surface of specific Gram-positive microbes. Type VII secretion is a non-canonical secretion pathway for WXG100 family proteins in mycobacteria. Gram-positive bacteria also secrete WXG100 proteins and carry unique genes that either contribute to discrete steps in secretion or represent distinctive substrates for protein transport reactions
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