50 research outputs found
Quorum Sensing of Acidophiles: A Communication System in Microorganisms
Communication is important for organisms living in nature. Quorum sensing system (QS) are intercellular communication systems that promote the sociality of microbes. Microorganisms could promote cell-to-cell cooperation and population density to adapt to the changing environment through QS-mediated regulation that is dependent on the secretion and the detection of signal molecules (or called autoinducers). QS system is also discovered in acidophiles, a microorganism that is widely used in the bioleaching industry and can live in an acidic environment. An example is the LuxI/R-like QS system (AfeI/R) that has been reported in the chemoautotrophic species of the genus Acidithiobacillus. In this chapter, we will introduce the types and distribution of the QS system, and the biological function and regulatory mechanism of QS in acidophiles. We will also discuss the potential ecological function of QS system and the application value of the QS system in the control and regulation of the bioleaching process in the related industries and acid mine damage
Co-production of pigment and high value-added bacterial nanocellulose from Suaeda salsa biomass with improved efficiency of enzymatic saccharification and fermentation
This study evaluated the co-production of pigment and bacterial nanocellulose (BNC) from S. salsa biomass. The extraction of the beet red pigment reduced the salts and flavonoids contents by 82.7%–100%, promoting the efficiencies of enzymatic saccharification of the biomass and the fermentation of BNC from the hydrolysate. SEM analysis revealed that the extraction process disrupted the lignocellulosic fiber structure, and the chemical analysis revealed the lessened cellulase inhibitors, consequently facilitating enzymatic saccharification for 10.4 times. BNC producing strains were found to be hyper-sensitive to NaCl stress, produced up to 400.4% more BNC from the hydrolysate after the extraction. The fermentation results of BNC indicated that the LDU-A strain yielded 2.116 g/L and 0.539 g/L in ES-M and NES-M, respectively. In comparison to the control, the yield in ES-M increased by approximately 20.0%, while the enhancement in NES-M was more significant, reaching 292.6%. After conducting a comprehensive characterization of BNC derived from S. salsa through Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Thermogravimetric Analysis (TGA), the average fiber diameter distribution of these four BNC materials ranges from 22.23 to 33.03 nanometers, with a crystallinity range of 77%–90%. Additionally, they exhibit a consistent trend during the thermal degradation process, further emphasizing their stability in high-temperature environments and similar thermal properties. Our study found an efficient co-production approach of pigment and BNC from S. salsa biomass. Pigment extraction made biomass more physically and chemically digestible to cellulase, and significantly improved BNC productivity and quality
A new bio-oxidation method for removing iron deposits from waterlogged wood of Nanhai I shipwreck, Guangdong, China
The widespread presence of iron and sulfur compounds such as pyrite in marine waterlogged archeological wood (WAW) can cause irreversible damage to the safety of its preservation. This issue has been a longstanding concern for cultural heritage conservation communities. In this study, we examined the distribution and phase composition of Fe and sulfur compounds in wood samples obtained from the Nanhai I shipwreck using ESEM-EDS, micro-Raman spectroscopy, and an X-ray diffractometer. The removal of iron from WAW samples of the Nanhai I shipwreck using Acidithiobacillus ferrooxidans (A. ferrooxidans) was evaluated using conductivity and ICP-AES analysis. The results showed that A. ferrooxidans effectively improved the removal of iron from WAW. The degradation of fresh healthy wood during treatment was also analyzed using infrared spectroscopy, and the results showed that the treatment had little effect on the samples over a short period. This study demonstrates, for the first time, the feasibility of iron extraction from marine WAW by A.ferrooxidans. This was also the first attempt in China to apply biological oxidation to the removal of iron from marine archeological materials
Acidithiobacillus caldus sulfur oxidation model based on transcriptome analysis between the wild type and sulfur oxygenase reductase defective mutant.
Acidithiobacillus caldus (A. caldus) is widely used in bio-leaching. It gains energy and electrons from oxidation of elemental sulfur and reduced inorganic sulfur compounds (RISCs) for carbon dioxide fixation and growth. Genomic analyses suggest that its sulfur oxidation system involves a truncated sulfur oxidation (Sox) system (omitting SoxCD), non-Sox sulfur oxidation system similar to the sulfur oxidation in A. ferrooxidans, and sulfur oxygenase reductase (SOR). The complexity of the sulfur oxidation system of A. caldus generates a big obstacle on the research of its sulfur oxidation mechanism. However, the development of genetic manipulation method for A. caldus in recent years provides powerful tools for constructing genetic mutants to study the sulfur oxidation system.An A. caldus mutant lacking the sulfur oxygenase reductase gene (sor) was created and its growth abilities were measured in media using elemental sulfur (S(0)) and tetrathionate (K(2)S(4)O(6)) as the substrates, respectively. Then, comparative transcriptome analysis (microarrays and real-time quantitative PCR) of the wild type and the Δsor mutant in S(0) and K(2)S(4)O(6) media were employed to detect the differentially expressed genes involved in sulfur oxidation. SOR was concluded to oxidize the cytoplasmic elemental sulfur, but could not couple the sulfur oxidation with the electron transfer chain or substrate-level phosphorylation. Other elemental sulfur oxidation pathways including sulfur diooxygenase (SDO) and heterodisulfide reductase (HDR), the truncated Sox pathway, and the S(4)I pathway for hydrolysis of tetrathionate and oxidation of thiosulfate in A. caldus are proposed according to expression patterns of sulfur oxidation genes and growth abilities of the wild type and the mutant in different substrates media.An integrated sulfur oxidation model with various sulfur oxidation pathways of A. caldus is proposed and the features of this model are summarized
Increasing RpoS expression causes cell death in Borrelia burgdorferi.
RpoS, one of the two alternative σ factors in Borrelia burgdorferi, is tightly controlled by multiple regulators and, in turn, determines expression of many critical virulence factors. Here we show that increasing RpoS expression causes cell death. The immediate effect of increasing RpoS expression was to promote bacterial division and as a consequence result in a rapid increase in cell number before causing bacterial death. No DNA fragmentation or degradation was observed during this induced cell death. Cryo-electron microscopy showed induced cells first formed blebs, which were eventually released from dying cells. Apparently blebbing initiated cell disintegration leading to cell death. These findings led us to hypothesize that increasing RpoS expression triggers intracellular programs and/or pathways that cause spirochete death. The potential biological significance of induced cell death may help B. burgdorferi regulate its population to maintain its life cycle in nature
The Essential Role of OmpR in <i>Acidithiobacillus caldus</i> Adapting to the High Osmolarity and Its Regulation on the Tetrathionate-Metabolic Pathway
Acidithiobacillus spp. are prevalent in acid mine drainage, and they have been widely used in biomining for extracting nonferrous metals from ores. The osmotic stress generated by elevated concentrations of inorganic ions is a severe challenge for the growth of Acidithiobacillus spp. in the bioleaching process; however, the adaptation mechanism of these bacteria to high osmotic pressure remains unclear. In this study, bioinformatics analysis indicated that the osmotic stress response two-component system EnvZ-OmpR is widely distributed in Acidithiobacillus spp., while OmpRs from Acidithiobacillus spp. exhibited a far more evolutionary relationship with the well-studied OmpRs in E. coli and Salmonella typhimurium. The growth measurement of an Acidithiobacillus caldus (A. caldus) ompR-knockout strain demonstrated that OmpR is essential in the adaptation of this bacterium to high osmotic stress. The overall impact of OmpR on the various metabolic and regulatory systems of A. caldus was revealed by transcriptome analysis. The OmpR binding sequences of differentially expressed genes (DEGs) were predicted, and the OmpR box motif in A. caldus was analysed. The direct and negative regulation of EnvZ-OmpR on the tetrathionate-metabolic (tetH) cluster in A. caldus was discovered for the first time, and a co-regulation mode mediated by EnvZ-OmpR and RsrS-RsrR for the tetrathionate intermediate thiosulfate-oxidizing (S4I) pathway in this microorganism was proposed. This study reveals that EnvZ-OmpR is an indispensable regulatory system for the ability of A. caldus to cope with high osmotic stress and the significance of EnvZ-OmpR on the regulation of sulfur metabolism in A. caldus adapting to the high-salt environment
Construction of novel pJRD215-derived plasmids using chloramphenicol acetyltransferase (cat) gene as a selection marker for Acidithiobacillus caldus.
Acidithiobacillus caldus, a Gram-negative, chemolithotrophic sulfur-oxidizing bacterium, is widely applied in bioleaching. The absence of an ideal selection marker has become a major obstacle to achieve high efficiency of the gene transfer system for A. caldus. Plasmid pJRD215, widely used in Acidithiobacillus spp., has severe drawbacks in molecular manipulations and potential biosafety issues due to its mobility. Therefore, finding a new selection marker and constructing new plasmids have become an urgent and fundamental work for A. caldus.Effective inhibitory effect of chloramphenicol on the growth of A. caldus was elucidated for the first time. The P2-cat gene cassette, including a chloramphenicol acetyltransferase gene (cat) from plasmid pACBSR and a promoter (P2) upstream of the tetracycline resistance gene on pBR322, was designed, chloramphenicol acetyltransferase was expressed in A. caldus, and the enzyme activity was assessed. A new vector pSDU1 carrying the replication and mobilization regions derived from pJRD215, the P2-cat gene cassette and a multiple cloning site from pUC19 was successfully constructed. Compared with pJRD215, pSDU1 had a 27-fold increase in electrotransformation efficiency (30.43±0.88×104 CFU/μg DNA for pSDU1 and 1.09±0.11×104 CFU/μg DNA for pJRD215), better carrying capacity and could offer more convenience for the restriction enzyme digestion. In addition, the generated plasmid pSDU1Δmob, a novel non-mobilizable derivative of pSDU1 lacking some DNA sequences involved in the mobilization process, had increased copy number in A. caldus and lost its mobility for biosafety considerations. Both pSDU1 and pSDU1Δmob exhibited stable maintenance in A. caldus within 50 passages. However, further deletion of orfEF region involved in regulating repAC operon resulted in a negative effect on transformation efficiency, copy number and stability of plasmid pSDU1ΔmobΔorfEF in A. caldus.Chloramphenicol was proved to be an ideal selection marker for A. caldus. Novel plasmids carrying cat gene were constructed. The utilization of these vectors will undoubtedly facilitate efficient genetic manipulations and accelerate the research progress in A. caldus