Bacterial biomass is considered as one of the central parameters in the research on marine ecosystems. Now, the methods to convert bacterial biomass could depend on bacterial volume, but there is some difference among the different conversion models. Not only the measurements of bacterial volume and bacterial carbon concentration, the conversion factor between the volume and bacterial biomass, but also the conversion model will be discussed in this paper. Conclusions can be reached that flow cytometry is available to assess bacterial volume and X ray microanalysis is the best method to measure single bacterial biomass and allometric model is widely used in conversion of biomass.

Anammox bacteria can perform anaerobic ammonium oxidation,a long missing process which contributes 30%~50% to dinitrogen gas in marine nitrogen cycling.The potential role of anam-mox bacteria coupling with ammonium oxidizing bacteria and archaea will benefit to elaborate the complex mechanism of marine nitrogen cycling.Furthermore,the unique cell and genomic characteris-tics make anammox bacteria an important model microorganism to explore the bacterial evolution.Here we reviewed the current status of molecular ecology of marine anammox bacteria and give a perspective into the future based on our understanding of the literature and our own work.