title: A comparative study of fatty acid profile and formation of biofilm in Geobacillus gargensis exposed to variable abiotic stress.
abstract: Understanding bacterial fatty acid (FA) profile has a great taxonomic significance as well as clinical importance for diagnosis issues. Both the composition and nature of membrane FAs change under different nutritional, biotic and (or) abiotic stresses, and environmental stress. Bacteria produce both odd-carbon as well as branched-chain fatty acids (BCFAs). This study was designed to examine the effect of abiotic pressure, including salinity, temperature, pH, and oxinic stress on the growth, development, and FA profile in thermophilic Geobacillus gargensis. Under these stresses, 3 parametric ratios, 2-methyl fatty acids/3-methyl fatty acids (iso-/anteiso-FAs), BCFAs/straight-chain saturated fatty acids (SCSFA), and SCSFAs/straight-chain unsaturated fatty acids (SCUFA), in addition to total lipids affected by variable stresses were measured. Our results indicate that the ratio of total iso-/anteiso-FAs increased at the acidic pH range of 4.1-5.2 and decreased with increasing pH. The reverse was true for salt stress when iso-/anteiso-FAs ratio increased with salt concentration. The BCFAs/SCSFAs and SCSFAs/SCUFAs ratios increased at neutral and alkaline pH and high salt concentration, reduced incubation time, and comparatively high temperature (55-65 °C) of the growth medium. The bacterial total lipid percentage deceased with increasing salt concentration, incubation period, but it increased with temperature. The formation of extracellular polymeric substances was observed under all stress conditions and with the addition of sodium dodecyl sulfate (2 and 5 mmol/L) to the growth medium. The membrane phospholipid composition of the bacterium was analyzed by thin-layer chromatography.
authors.affiliation: Department of Biological Sciences, Faculty of Science, Kuwait University, Kuwait.
authors.forename: Noor Essa
authors.initials: NE
authors.lastname: Al-Beloshei
authors.forename: Husain
authors.initials: H
authors.lastname: Al-Awadhi
authors.forename: Rania A
authors.initials: RA
authors.lastname: Al-Khalaf
authors.forename: Mohammad
authors.initials: M
authors.lastname: Afzal
mesh_terms: D018441:Biofilms; D002855:Chromatography, Thin Layer; D003470:Culture Media / Q000737:chemistry / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry* / Q000378:metabolism; D056506:Geobacillus / Q000737:chemistry* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D054712:Salinity; D012965:Sodium Chloride / Q000378:metabolism; D013312:Stress, Physiological
chemical_list: D003470:Culture Media; D005227:Fatty Acids; D012965:Sodium Chloride
keywords: Geobacillus gargensis; abiotic stress; acides gras à chaîne ramifiée; biofilm; branched-chain fatty acids; extracellular polymeric substances; stress abiotique; substances polymériques extracellulaires