Question

5) Denitrifiers use nitrite reductase genes for denitrification. You get hundreds of samples sent to you from habitats where denitrification is important. Describe how you would compare these samples and what would be different from the methods you outlined in your answer to number 4 above

7) Upwelling systems bring nitrate to the surface ocean, describe in detail the microbial consequences of this nutrient supply, it's implications below the surface ocean and the nitrogen cycling processes that dominate there. Use drawings if they help your answer

8) Describe ecological concepts as they apply to the human microbiome and how they frame comparisons between samples, groups of samples etc. How would you use these concepts to design the next set of studies following the infant microbiome. I expect you to do some legwork beyond your readings to comprehensively answer this question

Answer 1

Answer:- (5)

Nitrite reductase is the key enzyme in the dissimilatory denitrification chain, catalysing the reduction of NO2- to NO. NO is now accepted as a product of NO2- reduction and an obligatory intermediate in most denitrifers, it is furthure reduce to N2O by NO reductase.

Purification and characterisation of Nitrite reductase from several bacterial sources have shown that there are two distinct classes of dissimilatory Nitrite reductases that yeild NO as the main reaction product.

The reduction of the nitrogen (N) oxides, nitrate (NO3 - ) and nitrite (NO2 - ), to the gases nitric oxide (NO), nitrous oxide (N2O), and denitrogen (N2) is important to primary production, water quality, and the chemistry and physics of the atmosphere at ecosystem, landscape, regional and global scales are called Denitrification. Unfortunately, it is a miserable process to measure, Available methods are problematic for a variety of reasons, they change substrate concentrations, disturb the physical setting of the process,lack senstivity, or are prohibitively costly in time and expense. Most fundamentally, it is very difficult to quantify the dominant end product (N2) of denitrification given is high background concentration in the environment. Quantification of denitrification is also hindered by high spartial and temporal variation in the process, especially in terrestrial environments.