Carbon stable isotope patterns of cyclic terpenoids: A comparison of cultured alkaliphilic aerobic methanotrophic bacteria and methane-seep environments

Variation of salinity and nitrogen concentration affects the pentacyclic triterpenoid inventory of the haloalkaliphilic aerobic methanotrophic bacterium Methylotuvimicrobium alcaliphilum

“…The inventory of lipid biomarkers of the Type I methanotroph M. alcaliphilum has been previously described by Banta et al ( 2015 ), Rush et al ( 2016 ), and Cordova-Gonzalez et al ( 2020 ), although under different culturing conditions than those chosen in this study. Most abundant BHPs in M. alcaliphilum cultures are aminotriol ( IIIb ), 3-methyl-aminotriol ( IVb ), aminotetrol ( V ), and 3-methyl-aminotetrol ( VI ; Figs.…”

“…Harvested cells were freeze-dried and gently ground, then extracted with dichloromethane (DCM)/methanol (MeOH) (3:1, v / v ) by successive ultrasonication to produce the total lipid extract (TLE) according to Cordova-Gonzalez et al ( 2020 ). An aliquot of the TLE was acetylated by adding acetic acid anhydride/pyridine (1:1 v / v ) to the dried TLE at 60 °C for one hour and left at room temperature overnight.…”

“…Among the most specific capabilities of aerobic methanotrophs is their ability to synthesize a unique lipid biomarker inventory. Apart from fatty acids with characteristic double bond positions (e.g., Hanson and Hanson 1996 ), this group of bacteria is known as a producer of a variety of source-specific pentacyclic (hopanoids) and tetracyclic triterpenoids (steroids) (e.g., Bouvier et al 1976 ; Rohmer et al 1984 ; Talbot and Farrimond 2007 ; Banta et al 2015 ; Rush et al 2016 ; Wei et al 2016 ; Cordova-Gonzalez et al 2020 ). The cyclic triterpenoids are known to be crucial for cell functions such as cell growth and survival (Kannenberg and Poralla 1999 ; Welander et al 2009 ; Welander and Summons 2012 ).…”

“…Nalin et al ( 2000 ) have reported slightly increased hopanoid contents under nitrogen-replete (NH 4 + ) conditions for several nitrogen-fixing actinomycete Frankia strains. Even though some studies exist, our knowledge on the influence of environmental parameters on lipid production by methanotrophic bacteria is still limited, being based on only a few culture experiments (Jahnke et al 1999 ; Talbot et al 2001 ; Cordova-Gonzalez et al 2020 ). Often the interpretation of environmental samples is still challenging due to the lack of culture experiments under conditions close to those of the respective environments.…”

“…Here, we use cultivation experiments to assess whether changes in nitrate availability and salinity affect the composition and abundance of pentacyclic triterpenoids produced by the Type I methanotroph Methylotuvimicrobium alcaliphilum , a haloalkaliphilic strain, which has been studied previously for its triterpenoid inventory (Banta et al 2015 ; Rush et al 2016 ; Cordova-Gonzalez et al 2020 ). We report the occurrence of novel BHPs in M. alcaliphilum and modifications of its lipid inventory at varying salinities and nitrate concentrations.…”