Methanogens, sulphate and heavy metals: a complex system

Anaerobic digestion (AD) is a well-established technology used for the treatment of wastes and wastewaters with high organic content. During AD organic matter is converted stepwise to methane-containing biogasa renewable energy carrier. Methane production occurs in the last AD step and relies on methanogens, which are rather sensitive to some contaminants commonly found in wastewaters (e.g. heavy metals), or easily outcompeted by other groups of microorganisms (e.g. sulphate reducing bacteria, SRB). This review gives an overview of previous research and pilot-scale studies that shed some light on the effects of sulphate and heavy metals on methanogenesis. Despite the numerous studies on this subject, comparison is not always possible due to differences in the experimental conditions used and parameters explained. An overview of the possible benefits of methanogens and SRB co-habitation is also covered. Small amounts of sulphide produced by SRB can precipitate with metals, neutralising the negative effects of sulphide accumulation and free heavy metals on methanogenesis. Knowledge on how to untangle and balance sulphate reduction and methanogenesis is crucial to take advantage of the potential for the utilisation of biogenic sulphide as a metal detoxification agent with minimal loss in methane production in anaerobic digesters.The research was financially supported by the People Program (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/2007-2013 under REA agreement 289193

Determining Steady-State Kinetics of DNA Polymerase Nucleotide Incorporation

Polymerase enzymes catalyze the replication of DNA by incorporating deoxynucleoside monophosphates (dNMPs) into a primer strand in a 5′ to 3′ direction. Monitoring kinetic aspects of this catalytic process provides mechanistic information regarding polymerase-mediated DNA synthesis and the influences of nucleobase structure. For example, a range of polymerases have different capacities to synthesize DNA depending on the structure of the inserted dNMP (natural or synthetic) and also depending on the templating DNA base (modified vs. unmodified). Under steady-state conditions, relative rates depend on the deoxynucleoside triphosphate (dNTP) residence times in the ternary (polymerase-DNA-dNTP) complex. This chapter describes a method to measure steady-state incorporation efficiencies by which polymerase enzymes insert dNMPs into primer-template (P/T) oligonucleotides. The method described involves the use of a primer oligonucleotide 5′ radiolabeled with [γ-32P]ATP. Significant established applications of this experiment include studies regarding mechanisms of nucleotide misincorporation as a basis of chemically induced DNA mutation. Further, it can provide information important in various contexts ranging from biophysical to medical-based studies.ISSN:1064-3745ISSN:1940-602

Impact of sperm DNA chromatin in the clinic

The paternal contribution to fertilization and embryogenesis is frequently overlooked as the spermatozoon is often considered to be a silent vessel whose only function is to safely deliver the paternal genome to the maternal oocyte. In this article, we hope to demonstrate that this perception is far from the truth. Typically, infertile men have been unable to conceive naturally (or through regular IVF), and therefore, a perturbation of the genetic integrity of sperm heads in infertile males has been under-considered. The advent of intracytoplasmic sperm injection (ICSI) however has led to very successful treatment of male factor infertility and subsequent widespread use in IVF clinics worldwide. Until recently, little concern has been raised about the genetic quality of sperm in ICSI patients or the impact genetic aberrations could have on fertility and embryogenesis. This review highlights the importance of chromatin packaging in the sperm nucleus as essential for the establishment and maintenance of a viable pregnancy