Hopanoids in Cyanobacteria Biomass and Related Samples

Abstract Hopanoids are steroid-like compounds placed within large groups of pentacyclic triterpenoids. Such substances have been found as the substantial fraction of nonpolar substances within marine and terrestrial sediments. They are generally considered as useful biomarkers that allow fingerprinting and classification of biological, environmental, and geological samples. Hopanoids are considered as diagnostic or fossil biomarkers because their fingerprints provide principal information for geochemical and environmental research focusing on both modern and ancient investigations. Cyanobacteria are “ancient” microbes that belong to the group of prokaryotic and photosynthetic organisms. They form a fairly nonhomogeneous group of microorganisms possessing great molecular and morphological diversity and usually significantly contribute to the total biomass of sediments, reflecting environmental conditions during large-scale time geological processes. Hopanoid biomarkers can be particularly useful for analysis of the composition of bacterial ecosystems; for example, cyanobacteria and such biomarkers may indicate the existence of green algae–containing communities at the time of sediment deposition. This review describes current research concerning hopanoid profiling in cyanobacteria, mainly in samples originated from stromatolites, microbial biomass cultivated under different conditions as well as sediments and rock samples. Such biomarkers allow fingerprinting and classification of biological, environmental, and geological samples. We also demonstrate that multivariate approach for data analysis may significantly extend our knowledge concerning proper biomarker selection and samples classification based on hopanoids and related nonpolar compounds.