Bacterial nanotubes are membranous structures that have been reported to function as conduits between cells to exchange DNA, proteins, and nutrients. Here, we investigate the morphology and formation ...of bacterial nanotubes using Bacillus subtilis. We show that nanotube formation is associated with stress conditions, and is highly sensitive to the cells' genetic background, growth phase, and sample preparation methods. Remarkably, nanotubes appear to be extruded exclusively from dying cells, likely as a result of biophysical forces. Their emergence is extremely fast, occurring within seconds by cannibalizing the cell membrane. Subsequent experiments reveal that cell-to-cell transfer of non-conjugative plasmids depends strictly on the competence system of the cell, and not on nanotube formation. Our study thus supports the notion that bacterial nanotubes are a post mortem phenomenon involved in cell disintegration, and are unlikely to be involved in cytoplasmic content exchange between live cells.
The term “Glomalin” was originally used to describe a hypothetical gene product of arbuscular mycorrhizal fungi (AMF) that was assumed to be a nearly ubiquitous, thermostable and highly recalcitrant ...glycoprotein, deposited in soils in large amounts, and deemed to indicate soil health and quality. It was defined operationally as the fraction of soil organic matter (SOM) extractable by a hot citrate buffer and assessed either by Bradford assay or by cross-reactivity with monoclonal antibody MAb32B11. Later, it was recognized that the extracts contained a variety of compounds, including some of non-AMF origin, cross-reactive with both Bradford assay and the monoclonal antibody. This led to re-describing the pertinent (and still only operationally defined) SOM as “glomalin-related soil proteins (GRSP)”, albeit without any substantial change in the underlying concepts. Consequently, a great deal of confusion in this area arose among researchers in soil, plant, and environmental sciences. Glomalin or GRSP (often used interchangeably) has previously been linked to various soil features, including stability of soil aggregates, size of soil C and N pools, sequestration of heavy metals, and alleviation of various plant stresses. GRSP concentrations in soil often, but not always, have been correlated with AMF biomass measured by alternative (mainly microscopic) approaches. GRSP formation, deposition, and/or decomposition in soils seem to be largely dependent on a multitude of interactions among plants, AMF, and other soil microorganisms, including prokaryotes. The chemical structure of GRSP extracted from soil remains unclear and generally complex. That is due to the unspecific mode of its extraction and purification, as well as the great variety of analytical approaches that have been used heretofore to assess it. Future research needs to elucidate the exact composition of this operationally defined SOM fraction, the controls over its production and accumulation in soils, and its exact role in soil ecology generally and soil food webs in particular. Furthermore, novel and independent tools should be established to more specifically (as compared to current glomalin assays) assess AMF biomass and functioning in roots and soil and its involvement in soil processes.
•Glomalin is a hypothetical gene product of arbuscular mycorrhizal fungi (AMF).•It has been heralded as a suitable proxy for AMF abundance, activity and legacy.•In the past, glomalin has been defined operationally as a specific SOM fraction.•As such, glomalin contains materials produced by different processes and organisms.•Proxies with higher specificity than glomalin may thus be required in the future.
Three strains of a butyrate-producing bacterium were isolated from the rumen contents of grazing sheep and cows. The strains were anaerobic, with Gram-positive cell walls, ...straight-to-slightly-curved, rod-shaped, non-spore-forming and single flagellate. C
, C
, C
and C
were the predominant fatty acids. The cell-wall peptidoglycan type was A1
. The DNA G+C content varied from 41.4 to 42.2 mol%. 16S rRNA gene sequence similarities between the isolates and
,
and
were found to be 96, 95 and 95 %, respectively. The phylogenetic tree showed that the strains constituted a different taxon, separate from other taxa with validly published names and forming a cluster with strains of
On the basis of phenotypic, chemotaxonomic and phylogenetic results (16S RNA,
,
,
genes), the isolates are considered to represent a novel species of a new genus of the family
, for which the name
gen. nov., sp. nov. is proposed (type strain JK623
= DSM 29029
= LMG 28559
). We also propose the transfer of
to the new genus
gen. nov., comb nov. This new genus represents saccharoclastic, chemo-organotrophic and obligatory anaerobic, non-spore-forming rods with Gram-positive membrane. The main fermentation products on peptone yeast glucose (PYG) medium were butyrate, acetate, hydrogen and lactate. The type species of the genus is
gen. nov., comb nov. (Prévot, 1938) with type strain ATCC 33656
( = JCM 17463
).
Spore awakening is a series of actions that starts with purely physical processes and continues via the launching of gene expression and metabolic activities, eventually achieving a vegetative phase ...of growth. In spore-forming microorganisms, the germination process is controlled by intra- and inter-species communication. However, in the
clade, which is capable of developing a plethora of valuable compounds, the chemical signals produced during germination have not been systematically studied before. Our previously published data revealed that several secondary metabolite biosynthetic genes are expressed during germination. Therefore, we focus here on the secondary metabolite production during this developmental stage. Using high-performance liquid chromatography-mass spectrometry, we found that the sesquiterpenoid antibiotic albaflavenone, the polyketide germicidin A, and chalcone are produced during germination of the model streptomycete,
. Interestingly, the last two compounds revealed an inhibitory effect on the germination process. The secondary metabolites originating from the early stage of microbial growth may coordinate the development of the producer (
) and/or play a role in competitive microflora repression (
) in their nature environments.
The alarming rise of bacterial antibiotic resistance requires the development of new compounds. Such compounds, lipophosphonoxins (LPPOs), were previously reported to be active against numerous ...bacterial species, but serum albumins abolished their activity. Here we describe the synthesis and evaluation of novel antibacterial compounds termed LEGO-LPPOs, loosely based on LPPOs, consisting of a central linker module with two attached connector modules on either side. The connector modules are then decorated with polar and hydrophobic modules. We performed an extensive structure–activity relationship study by varying the length of the linker and hydrophobic modules. The best compounds were active against both Gram-negative and Gram-positive species including multiresistant strains and persisters. LEGO-LPPOs act by first depleting the membrane potential and then creating pores in the cytoplasmic membrane. Importantly, their efficacy is not affected by the presence of serum albumins. Low cytotoxicity and low propensity for resistance development demonstrate their potential for therapeutic use.
Layered crystal structures tend to form flat platelet-like crystallites, and nanofibers having such a structure exhibit strip-like morphology. Crystallographic plane forming the dominant flat surface ...of the nanofibers can be used for surface modification with catalytically active nanoparticles capable of anchoring to the dominant flat surface. In this study, polyvinylidene fluoride (PVDF) nanofibers exhibiting strip-like morphology and longitudinal folding were prepared using wire electrospinning, and surface modified with CeO2 nanoparticles. Experimental characterization of the CeO2/PVDF membrane using (high-resolution) scanning electron microscopy and X-ray photoelectron spectroscopy was supplemented by a force field-based molecular modeling. The modeling has shown that the dominant PVDF(100) plane is suitable for anchoring the CeO2 nanoparticles. In this respect, the PVDF(100) plane is comparable to the less exposed fluorine-oriented PVDF(010) plane, and both planes show stronger interaction with CeO2 compared to hydrogen-oriented PVDF(010) plane. Molecular modeling also revealed preferred crystallographic orientations of anchored CeO2 nanoparticles: these are the catalytically active planes (100), (110), and (111). The successful surface modification and the finding that CeO2 nanoparticles on the dominant PVDF(100) surface can preferentially exhibit these crystallographic orientations thus provides the possibility of various practical applications of the CeO2/PVDF membrane.
•Flat strip-like PVDF nanofibers were surface modified with CeO2 nanoparticles.•PVDF-CeO2 interactions were studied by molecular modeling for various (hkl) planes.•The dominant PVDF(100) surface of nanofibers is suitable for anchoring of CeO2.•Preferred orientations of CeO2 – (100), (110), (111) – on PVDF were revealed.
Display omitted
•Sea urchin extracellular proteins drive PVP–AuNPs stability and related aggregation kinetic.•PVP–AuNPs excite sea urchin immune cell phagocytic activity.•PVP–AuNP-exposed immune ...cells use metabolic rewiring to control inflammation.•The sea urchin Immunological response involves TLR4/ERK signalling pathway.•Sea urchin immune cells show a PVP–AuNP tolerogenic immunological response.
We report that the immunogenicity of colloidal gold nanoparticles coated with polyvinylpyrrolidone (PVP–AuNPs) in a model organism, the sea urchin Paracentrotus lividus, can function as a proxy for humans for in vitro immunological studies. To profile the immune recognition and interaction from exposure to PVP–AuNPs (1 and 10 μg mL−1), we applied an extensive nano-scale approach, including particle physicochemical characterisation involving immunology, cellular biology, and metabolomics. The interaction between PVP–AuNPs and soluble proteins of the sea urchin physiological coelomic fluid (blood equivalent) results in the formation of a protein “corona” surrounding the NPs from three major proteins that influence the hydrodynamic size and colloidal stability of the particle. At the lower concentration of PVP–AuNPs, the P. lividus phagocytes show a broad metabolic plasticity based on the biosynthesis of metabolites mediating inflammation and phagocytosis. At the higher concentration of PVP–AuNPs, phagocytes activate an immunological response involving Toll-like receptor 4 (TLR4) signalling pathway at 24 hours of exposure. These results emphasise that exposure to PVP–AuNPs drives inflammatory signalling by the phagocytes and the resolution at both the low and high concentrations of the PVP–AuNPs and provides more details regarding the immunogenicity of these NPs.
How bacteria control proper septum placement at midcell, to guarantee the generation of identical daughter cells, is still largely unknown. Although different systems involved in the selection of the ...division site have been described in selected species, these do not appear to be widely conserved. Here, we report that LocZ (Spr0334), a newly identified cell division protein, is involved in proper septum placement in Streptococcus pneumoniae. We show that locZ is not essential but that its deletion results in cell division defects and shape deformation, causing cells to divide asymmetrically and generate unequally sized, occasionally anucleated, daughter cells. LocZ has a unique localization profile. It arrives early at midcell, before FtsZ and FtsA, and leaves the septum early, apparently moving along with the equatorial rings that mark the future division sites. Consistently, cells lacking LocZ also show misplacement of the Z-ring, suggesting that it could act as a positive regulator to determine septum placement. LocZ was identified as a substrate of the Ser/Thr protein kinase StkP, which regulates cell division in S. pneumoniae. Interestingly, homologues of LocZ are found only in streptococci, lactococci, and enterococci, indicating that this close phylogenetically related group of bacteria evolved a specific solution to spatially regulate cell division.
Bacterial cell division is a highly ordered process regulated in time and space. Recently, we reported that the Ser/Thr protein kinase StkP regulates cell division in Streptococcus pneumoniae, through phosphorylation of several key proteins. Here, we characterized one of the StkP substrates, Spr0334, which we named LocZ. We show that LocZ is a new cell division protein important for proper septum placement and likely functions as a marker of the cell division site. Consistently, LocZ supports proper Z-ring positioning at midcell. LocZ is conserved only among streptococci, lactococci, and enterococci, which lack homologues of the Min and nucleoid occlusion effectors, indicating that these bacteria adapted a unique mechanism to find their middle, reflecting their specific shape and symmetry.
RNase J1 is the major 5′‐to‐3′ bacterial exoribonuclease. We demonstrate that in its absence, RNA polymerases (RNAPs) are redistributed on DNA, with increased RNAP occupancy on some genes without a ...parallel increase in transcriptional output. This suggests that some of these RNAPs represent stalled, non‐transcribing complexes. We show that RNase J1 is able to resolve these stalled RNAP complexes by a “torpedo” mechanism, whereby RNase J1 degrades the nascent RNA and causes the transcription complex to disassemble upon collision with RNAP. A heterologous enzyme, yeast Xrn1 (5′‐to‐3′ exonuclease), is less efficient than RNase J1 in resolving stalled Bacillus subtilis RNAP, suggesting that the effect is RNase‐specific. Our results thus reveal a novel general principle, whereby an RNase can participate in genome‐wide surveillance of stalled RNAP complexes, preventing potentially deleterious transcription–replication collisions.
Synopsis
Bacillus subtilis RNase J1 helps resolve stalled RNA polymerase (RNAP) elongation complexes on DNA by degrading RNA and dissociating the transcription complex. This “torpedo” mechanism likely contributes to prevention of transcription‐replication clashes and helps maintain genome integrity.
Deletion of RNase J1 strongly affects expression of one‐third of B. subtilis genes.
RNase J1 disassembles stalled transcription elongation complexes.
The activity of RNase J1 helps prevent transcription‐replication clashes.
Nascent RNA degradation by RNase J1 invokes disassembly of bacterial transcription complex upon collision with RNA polymerase.
PDF
