A method of water-soluble solid fraction saturation concentration evaluation in dry thalli of Antarctic lichenized fungi, in vivo

Abstract

BackgroundAt initial steps of rehydration from cryptobiosis of anhydrobiotic organisms or at rehydration of dry tissues the liquid 1H NMR signal increased anomaly. The surplus in liquid signal may appear if some solid constituents dissolved, or if they were decomposed by enzymatic action.MethodsHydration kinetics, sorption isotherm, 1H NMR spectra and high power relaxometry were applied to monitor gaseous phase rehydration of Antarctic lichen Cetraria aculeata. Tightly and loosely bound water signal were distinguished, and the upper hydration limit for dissolution of water soluble solid fraction was not observed. A simple theoretical model was proposed.ResultsThe hydration courses showed a very tightly bound water fraction, a tightly bound water, and a loosely bound water fraction. Sigmoidal in form sorption isotherm was fitted well by multilayer sorption model. 1H NMR showed one Gaussian signal component from solid matrix of thallus and one or two Lorentzian line components from tightly bound, and from loosely bound water. The hydration dependency of liquid signal was fitted by rational function.ConclusionsAlthough in dehydrated C.aculeata the level of carbohydrates and polyols was low, the lichenase action during rehydration process increased it; the averaged saturation concentration cs=(57.3±12.0)%, which resembled that for sucrose.General significanceThe proposed method of water soluble solid fraction saturation concentration, cs, calculation from 1H NMR data may be applied for other organisms experiencing extreme dehydration or for dry tissues. We recalculated the published elsewhere data for horse chestnut (Aesculus hippocastanum) bast [water-soluble solid fraction recognized as sucrose, cs=(74.5±5.1)%]; and for Usnea antarctica, where cs=0.81±0.04.

A comparative analysis of gaseous phase hydration properties of two lichenized fungi: Niebla tigrina (Follman) Rundel & Bowler from Atacama Desert and Umbilicaria antarctica Frey & I. M. Lamb from Robert Island, Southern Shetlands Archipelago, maritime Antarctica

“…The hydration dependence of mobile proton signal amplitude expressed in units of solid signal amplitude, L/S , measured for U. antarctica thalli in whole range of hydration levels investigated, and for N. tigrina thalli for initial part of hydration range is not linear in form (Fig. 9 a, b), and is fitted well by a rational function (Harańczyk et al 2016 ; Bacior et al 2017 ). The surplus in mobile 1 H-NMR signal component may be caused by a presence of solid water soluble fraction of thallus, which dissolves with the increased hydration level of the sample.…”

“…For polyols such a value is quite similar and equals γ = 0.715 ± 0.063. If the type of water-soluble solid fraction is not known, the mean value averaged over sugars and polyols is equal γ = 0.657(83) (Harańczyk et al 2016 ). This allows one the successful fitting of saturation concentration for water soluble solid fraction in unknown lichen.…”

“…Hydration time of tightly bound water fraction in U. antarctica resembles those for Ramalina terebrata with t 1 h = 1.24(24) h, (Harańczyk et al 2012b ) for Leptogium puberulum from King George Island, with t 1 h = 1.6(3) h (Hamada et al 1994 ), and for Turgidosculum complicatulum with t 1 h = 1.45(21) h (Bacior et al 2017 ). Among the species from Antarctica only Cetraria aculeata from Penguin Island with the hydration time of tightly bound water equal to t 1 h = 0.43(10) h (Harańczyk et al 2016 ) resembles that for N. tigrina from Atacama Desert.…”

“…In thalli of some Antarctic lichen species the 1 H-NMR experiments reveal an unexpected surplus in mobile proton signal appearing with the increased hydration level during a mild rehydration course performed from gaseous phase. This effect may be caused by two reasons, namely, by a simple dilution of water soluble solid fraction, as it is observed in some plant tissues (Harańczyk et al 1999 ) by lichenase-induced lichenin decomposition, which is observed in thalli of lichenized fungi (Harańczyk et al 2016 ; Bacior et al 2017 ); or for higher plants at initial phases of seed imbibition (Harańczyk et al 1996 ).…”

“…The supposed lichenin and isolichenin hydrolysis effectivity observed by these authors at rehydration of Antarctic lichens detected as a dissolution process of water soluble solid fraction extends for hydration levels, Δ m/m 0 , up to ca. 0.8 (Haranczyk et al 2016 ). The hypotesis was that in lichens populating dry habitats such a process may be not so much effective.…”