Both DNA gyrase and reverse gyrase are present in the hyperthermophilic bacterium Thermotoga maritima

Like all hyperthermophiles yet tested, the bacterium Thermotoga maritima contains a reverse gyrase. Here we show that it contains also a DNA gyrase. The genes top2A and top2B encoding the two subunits of a DNA gyrase-like enzyme have been cloned and sequenced. The Top2A (type II DNA topoisomerase A protein) is more similar to GyrA (DNA gyrase A protein) than to ParC [topoisomerase IV (Topo IV) C protein]. The difference is especially striking at the C-terminal domain, which differentiates DNA gyrases from Topo IV. DNA gyrase activity was detected in T. maritima and purified to homogeneity using a novobiocin-Sepharose column. This hyperhermophilic DNA gyrase has an optimal activity around 82–86°C. In contrast to plasmids from hyperthermophilic archaea, which are from relaxed to positively supercoiled, we found that the plasmid pRQ7 from Thermotoga sp. RQ7 is negatively supercoiled. pRQ7 became positively supercoiled after addition of novobiocin to cell cultures, indicating that its negative supercoiling is due to the DNA gyrase of the host strain. The findings concerning DNA gyrase and negative supercoiling in Thermotogales put into question the role of reverse gyrase in hyperthermophiles.

Two enzymes of diacylglyceryl-O-4′-(N,N,N,-trimethyl)homoserine biosynthesis are encoded by btaA and btaB in the purple bacterium Rhodobacter sphaeroides

Betaine lipids are ether-linked, nonphosphorous glycerolipids that resemble the more commonly known phosphatidylcholine in overall structure. Betaine lipids are abundant in many eukaryotes such as nonseed plants, algae, fungi, and amoeba. Some of these organisms are entirely devoid of phosphatidylcholine and, instead, contain a betaine lipid such as diacylglyceryl-O-4′-(N,N,N,-trimethyl)homoserine. Recently, this lipid also was discovered in the photosynthetic purple bacterium Rhodobacter sphaeroides where it seems to replace phosphatidylcholine under phosphate-limiting growth conditions. This discovery provided the opportunity to study the biosynthesis of betaine lipids in a bacterial model system. Mutants of R. sphaeroides deficient in the biosynthesis of the betaine lipid were isolated, and two genes essential for this process, btaA and btaB, were identified. It is proposed that btaA encodes an S-adenosylmethionine:diacylglycerol 3-amino-3-carboxypropyl transferase and btaB an S-adenosylmethionine-dependent N-methyltransferase. Both enzymatic activities can account for all reactions of betaine lipid head group biosynthesis. Because the equivalent reactions have been proposed for different eukaryotes, it seems likely that orthologs of btaA/btaB may be present in other betaine lipid-containing organisms.

Mucosal and systemic immune responses to a recombinant protein expressed on the surface of the oral commensal bacterium Streptococcus gordonii after oral colonization.

To circumvent the need to engineer pathogenic microorganisms as live vaccine-delivery vehicles, a system was developed which allowed for the stable expression of a wide range of protein antigens on the surface of Gram-positive commensal bacteria. The human oral commensal Streptococcus gordonii was engineered to surface express a 204-amino acid allergen from hornet venom (Ag5.2) as a fusion with the anchor region of the M6 protein of Streptococcus pyogenes. The immunogenicity of the M6-Ag5.2 fusion protein was assessed in mice inoculated orally and intranasally with a single dose of recombinant bacteria, resulting in the colonization of the oral/pharyngeal mucosa for 10-11 weeks. A significant increase of Ag5.2-specific IgA with relation to the total IgA was detected in saliva and lung lavages when compared with mice colonized with wild-type S. gordonii. A systemic IgG response to Ag5.2 was also induced after oral colonization. Thus, recombinant Gram-positive commensal bacteria may be a safe and effective way of inducing a local and systemic immune response.

Selection of the N-Acylhomoserine Lactone-Degrading Bacterium Alteromonas stellipolaris PQQ-42 and of Its Potential for Biocontrol in Aquaculture

The production of virulence factors by many pathogenic microorganisms depends on the intercellular communication system called quorum sensing, which involves the production and release of signal molecules known as autoinducers. Based on this, new-therapeutic strategies have emerged for the treatment of a variety of infections, such as the enzymatic degradation of signaling molecules, known as quorum quenching (QQ). In this study, we present the screening of QQ activity amongst 450 strains isolated from a bivalve hatchery in Granada (Spain), and the selection of the strain PQQ-42, which degrades a wide range of N-acylhomoserine lactones (AHLs). The selected strain, identified as Alteromonas stellipolaris, degraded the accumulation of AHLs and reduced the production of protease and chitinase and swimming motility of a Vibrio species in co-cultivation experiments in vitro. In the bio-control experiment, strain PQQ-42 significantly reduced the pathogenicity of Vibrio mediterranei VibC-Oc-097 upon the coral Oculina patagonica showing a lower degree of tissue damage (29.25 ± 14.63%) in its presence, compared to when the coral was infected with V. mediterranei VibC-Oc-097 alone (77.53 ± 13.22%). Our results suggest that this AHL-degrading bacterium may have biotechnological applications in aquaculture.

Über einen Fall von embolischer, eitriger Nephritis und Pneumonie bei einem Saugfohlen, hervorgerufen durch das Bacterium lactis aerogenes.

Inaug.-diss.--Hannover, 1912.

Protein film voltammetry of arsenite oxidase from the chemolithoautotrophic arsenite-oxidizing bacterium NT-26

The chemolithoautotrophic bacterium NT-26 (isolated from a gold mine in the Northern Territory of Australia) is unusual in that it acquires energy by oxidizing arsenite to arsenate while most other arsenic-oxidizing organisms perform this reaction as part of a detoxification mechanism against the potentially harmful arsenite [present as As(OH)(3) at neutral pH]. The enzyme that performs this reaction in NT-26 is the molybdoenzyme arsenite oxidase, and it has been previously isolated and characterized. Here we report the direct (unmediated) electrochemistry of NT-26 arsenite oxidase confined to the surface of a pyrolytic graphite working electrode. We have been able to demonstrate that the enzyme functions natively while adsorbed on the electrode where it displays stable and reproducible catalytic electrochemistry in the presence of arsenite. We report a pH dependence of the catalytic electrochemical potential of -33 mV/pH unit that is indicative of proton-coupled electron transfer. We also have performed catalytic voltammetry at a number of temperatures between 5 and 25 degrees C, and the catalytic current (proportional to the turnover number) follows simple Arrhenius behavior.

Enzymatic profiling of cellulosomal enzymes from the human gut bacterium, Ruminococcus champanellensis, reveals a fine-tuned system for cohesin-dockerin recognition

Funded by United States-Israel Binational Science Foundation (BSF), Jerusalem, Israel Israel Science Foundation (ISF). Grant Number: 1349 Israel Science Foundation Israel Strategic Alternative Energy Foundation (I-SAEF) BBSRC. Grant Number: BB/L009951/1 Scottish Government Food, Land and People program Society for Applied Microbiology

Enzymatic profiling of cellulosomal enzymes from the human gut bacterium, Ruminococcus champanellensis, reveals a fine-tuned system for cohesin-dockerin recognition

Funded by United States-Israel Binational Science Foundation (BSF), Jerusalem, Israel Israel Science Foundation (ISF). Grant Number: 1349 Israel Science Foundation Israel Strategic Alternative Energy Foundation (I-SAEF) BBSRC. Grant Number: BB/L009951/1 Scottish Government Food, Land and People program Society for Applied Microbiology

Biological fluorination from the sea : discovery of a SAM-dependent nucleophilic fluorinating enzyme from the marine-derived bacterium Streptomyces xinghaiensis NRRL B24674

We thank Prof. David O’Hagan and Dr Qingzhi Zhang (University of St Andrews, UK) for their helpful discussion and for providing the synthetic 50 -FDA sample. This work is supported by National Natural Science Foundation of China (No. 81503086), a starting funding (No. 20140520) from Tianjin University of Science & Technology, a research funding of “1000 Talents Plan” of Tianjin (to LM) and Foundation of Key Laboratory of Industrial Fermentation Microbiology of Ministry of Education and Tianjin Key Lab of Industrial Microbiology (No. 2015IM106)

Characterization of a new toxin from the entomopathogenic fungus Metarhizium anisopliae: the ribotoxin anisoplin

Metarhizium anisopliae is an entomopathogenic fungus relevant in biotechnology with applications like malaria vector control. Studies of its virulence factors are therefore of great interest. Fungal ribotoxins are toxic ribonucleases with extraordinary efficiency against target ribosomes and suggested as potential insecticides. Here, we describe this ribotoxin characteristic activity in M. anisopliae cultures. Anisoplin has been obtained as a recombinant protein and further characterized. It is structurally similar to hirsutellin A, the ribotoxin from the entomopathogen Hirsutella thompsonii. Moreover, anisoplin shows the ribonucleolytic activity typical of ribotoxins and cytotoxicity against insect cells. How Metarhizium uses this toxin and possible applications are on perspective.

Draft Genome Sequence of Staphylococcus succinus Strain CSM-77, a Moderately Halophilic Bacterium Isolated from a Triassic Salt Mine.

Here, we report the draft genome sequence of Staphylococcus succinus strain CSM-77. This moderately halophilic bacterium was isolated from the surface of a halite sample obtained from a Triassic salt mine.