Methane-oxidising microorganisms Classification and habitat requirements

1 Methane-oxidising microorganisms Classification and habitat requirements 

Figxire 5.2 Taxonomic affiliation of methanotrophs (Trotsenko Stfpniewska, 2012). 

Methanotrophic bacteria are widespread in nature. They inhabit all upland, semi-aquatic and aquatic environments of different climate zones. Methanotrophic bacteria or the effects of their activities were observed in arable soils (Hiitsch, 1998, Arif et al. 1996, Knief et al. 2005), forest soils (Reay et al. 2001, Wang Ineson, 2003, Knief et al. 2005), meadow soils (Bender Conrad, 1993, Horz et al. 2002, Abell et al. 2009), peat soils (Sundh et al. 1995 Mac Donald et al. 1996), rice paddy soils (Kolb et al. 2003, Macalady et al. 2002) in lake sediments (Auman et al. 2000, Costello et al. 2002) and sea sediments (Yan et al. 2006). Moreover, methanotrophs frequently occur in landfill cover soils (Wise et al. 1999, Kallistova et al. 2007, Cebron et al. 2007). They were also isolated from geothermal waters, hot springs (Tsubota et al. 2005, Dunfield et al. 2007), and soda lakes (Khmelenina et al. 1997). 

5-10 (Trotsenko Khmelenina, 2002). What is more, methanotrophic bacteria belonging to Verrucomicrobia which oxidised methane at pH 3.5 (Islam et al. 2008), at pH of 2-2.5 (Dunfield et al. 2007), and even at pH 1 (Pol et al. 2007) were also isolated. Most of the methanotrophs prefer the environment of low sahnity (Hanson Hanson, 1996). However, the methanotrophic bacteria Methylobacter alcaliphilus 20Z, Methylobacter modesto-halophilus lOS), which grew in the environment of NaCl concentration equalled to 8-9% (Kalyuzhnaya et al. 1999, Khmelenina et al. 1997) were found. 

Availability of methane determines quality of methanotrophic community. Soils incubated in the atmosphere enriched with methane (10% vol.) showed high capacity for methane oxidation but they do not show the ability to oxidize methane at atmospheric (ambient) concentration (Walkiewicz et al. 2012). This phenomenon can result from the presence of the type II methanotrophs in soils. Those methanotrophs have methanotrophic maximum activity and a low affinity to CH (high value of the Michaelis constant Kj ) (Bender Conrad, 1993). Both the parameters are determined on the base of Michaelis-Menten equation. K constant represents the substrate concentration at which the rate of an enzyme-catalysed reaction is half of the maximum value. The type II bacteria are isolated from the environments rich in methane ( 1%) and poor in oxygen (about 1%) (Hanson Hanson, 1996), such as bog peat or landfill covers. They are less sensitive to the environmental changes than the type I bacteria which has a low value of and high affinity to methane (Henckel et al. 2000) proved by the low value 

---