The recent revision of the Acidithiobacillia class using genomic taxonomy methods has shown that, in addition to the existence of previously unrecognized genera and species, some species of the class harbor levels of divergence that are congruent with ongoing differentiation processes. In this study, we have performed a subspecies-level analysis of sequenced strains of Acidithiobacillus ferrooxidans to prove the existence of distinct sublineages and identify the discriminant genomic/genetic characteristics linked to these sublineages, and to shed light on the processes driving such differentiation. Differences in the genomic relatedness metrics, levels of synteny, gene content, and both integrated and episomal mobile genetic elements (MGE) repertoires support the existence of two subspecies-level taxa within A. ferrooxidans. While sublineage 2A harbors a small plasmid related to pTF5, this episomal MGE is absent in sublineage 2B strains. Likewise, clear differences in the occurrence, coverage and conservation of integrated MGEs are apparent between sublineages. Differential MGE-associated gene cargo pertained to the functional categories of energy metabolism, ion transport, cell surface modification, and defense mechanisms. Inferred functional differences have the potential to impact long-term adaptive processes and may underpin the basis of the subspecies-level differentiation uncovered within A. ferrooxidans. Genome resequencing of iron- and sulfur-adapted cultures of a selected 2A sublineage strain (CCM 4253) showed that both episomal and large integrated MGEs are conserved over twenty generations in either growth condition. In turn, active insertion sequences profoundly impact short-term adaptive processes. The ISAfe1 element was found to be highly active in sublineage 2A strain CCM 4253. Phenotypic mutations caused by the transposition of ISAfe1 into the pstC2 encoding phosphate-transport system permease protein were detected in sulfur-adapted cultures and shown to impair growth on ferrous iron upon the switch of electron donor. The phenotypic manifestation of the △pstC2 mutation, such as a loss of the ability to oxidize ferrous iron, is likely related to the inability of the mutant to secure the phosphorous availability for electron transport-linked phosphorylation coupled to iron oxidation. Depletion of the transpositional △pstC2 mutation occurred concomitantly with a shortening of the iron-oxidation lag phase at later transfers on a ferrous iron-containing medium. Therefore, the pstII operon appears to play an essential role in A. ferrooxidans when cells oxidize ferrous iron. Results highlight the influence of insertion sequences and both integrated and episomal mobile genetic elements in the short- and long-term adaptive processes of A. ferrooxidans strains under changing growth conditions.
Mycotoxins are secondary metabolites produced by several species of fungi, including the Fusarium, Aspergillus, and Penicillium species. Currently, more than 300 structurally diverse mycotoxins are known, including a group called minor mycotoxins, namely enniatins, beauvericin, and fusaproliferin. Beauvericin and enniatins possess a variety of biological activities. Their antimicrobial, antibiotic, or ionoforic activities have been proven and according to various bioassays, they are believed to be toxic. They are mainly found in cereal grains and their products, but they have also been detected in forage feedstuff. Mycotoxins in feedstuffs of livestock animals are of dual concern. First one relates to the safety of animal-derived food. Based on the available data, the carry-over of minor mycotoxins from feed to edible animal tissues is possible. The second concern relates to detrimental effects of mycotoxins on animal health and performance. This review aims to summarize current knowledge on the relation of minor mycotoxins to livestock animals.
The switch from aerobic to anaerobic respiration in the bacterium Paracoccus denitrificans is orchestrated by the action of three FNR-type transcription regulators FnrP, NNR and NarR, which are sensors for oxygen, nitric oxide and nitrite, respectively. In this work, we analyzed the protein composition of four strains (wild type, FnrP-, NNR- and NarR-mutant strains) grown aerobically, semiaerobically and semiaerobically in the presence of nitrate to discover the global role of FNR-family transcription regulators using proteomics, with data validation at the transcript and genome levels. Expression profiles were acquired using two-dimensional gel electrophoresis for 737 protein spots, in which 640 proteins were identified using mass spectrometry. The annotated 2-D proteome map provided the most comprehensive coverage of P. denitrificans proteome available to-date and can be accessed on-line at http://www.mpiib-berlin.mpg.de/2D-PAGE/. Our results revealed several types of regulation under the conditions tested: (1) FnrP-controlled regulation of nitrous oxide reductase, UspA and OmpW as confirmed at protein, transcript and DNA level (position of FNR boxes). (2) Proteins regulated via additional regulators, including proteins involved in NNR and NarR regulons: nitrate reductase beta-subunit, TonB-dependent receptors, nitrite reductase, a TenA-type transcription regulator, and an unknown protein with an alpha/beta hydrolase fold. (3) Proteins whose expression was affected mainly by the growth condition. This group contains SSU ribosomal protein S305 / sigma(54) modulation protein, and two short-chain reductase-dehydrogenase proteins.
- MeSH
- aerobióza fyziologie MeSH
- anaerobióza fyziologie MeSH
- bakteriální proteiny metabolismus MeSH
- dusitany metabolismus MeSH
- genetická transkripce fyziologie MeSH
- kyslík metabolismus MeSH
- oxid dusnatý metabolismus MeSH
- Paracoccus denitrificans fyziologie MeSH
- proteomika MeSH
- regulace genové exprese u bakterií fyziologie MeSH
- transkripční faktory metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
