Benefits of tropical peatland rewetting for subsidence reduction and forest regrowth: results from a large-scale restoration trial.

Drainage and deforestation of tropical peat swamp forests (PSF) in Southeast Asia cause carbon emissions and biodiversity loss of global concern. Restoration efforts to mitigate these impacts usually involve peatland rewetting by blocking canals. However, there have been no studies to date of the optimal rewetting approach that will reduce carbon emission whilst also promoting PSF regeneration. Here we present results of a large-scale restoration trial in Sumatra (Indonesia), monitored for 7.5 years. Water levels in a former plantation were raised over an area of 4800 ha by constructing 257 compacted peat dams in canals. We find peat surface subsidence rates in the rewetted restoration area and adjoining PSF to be halved where water tables were raised from ~ - 0.6 m to ~ - 0.3 m, demonstrating the success of rewetting in reducing carbon emission. A total of 57 native PSF tree species were found to spontaneously grow in the most rewetted conditions and in high densities, indicating that forest regrowth is underway. Based on our findings we propose that an effective PSF restoration strategy should follow stepwise rewetting to achieve substantial carbon emission reduction alongside unassisted regrowth of PSF, thereby enabling the peat, forest and canal vegetation to establish a new nature-based ecosystem balance.

Lipids shed into the culture medium by trypomastigotes of Trypanosoma cruzi.

Trypomastigote forms of Trypanosoma cruzi were metabolically labeled with [14C]-ethanolamine and [3H]-palmitic acid. Lipids shed to the culture medium were analyzed and compared with the parasite components. Phosphatidylcholine and lysophosphatidylcholine accounted for 53% of the total incorporated precursor. Interestingly, phosphatidylethanolamine and its lyso derivative lysophosphatidylethanolamine, although present in significant amounts in the parasites, could not be detected in the shed material. Shed lipids were highly enriched in the desaturated fatty acids C16:1 and C18:1 when compared to the total fatty acid pool isolated from the parasites.

Structure of the glycosylphosphatidylinositol-anchor of the trans-sialidase from Trypanosoma cruzi metacyclic trypomastigote forms.

Both, culture-derived and metacyclic trypomastigotes of Trypanosoma cruzi shed a glycoprotein, the shed acute phase antigen, that is responsible for the trans-sialidase activity. In the present work the structure of the glycosylphosphatidylinositol membrane anchor of the trans-sialidase isolated from metacyclic forms was determined. Parasites were metabolically labelled with [9, 10(n)3H]-palmitic acid and the glycoprotein was purified by immunoprecipitation with a monoclonal antibody directed against the repetitive aminoacid sequence. Treatment of the glycoprotein with phosphatidylinositol phospholipase C (PI-PLC) from Bacillus thuringiensis rendered a lipid that comigrated in TLC with a standard of ceramide. No alkylglycerol was detected in contrast with the results previously obtained for the trans-sialidase isolated from culture-derived trypomastigotes where both lipids were found. Chemical and chromatographic analysis showed that the lipid moiety is palmitoyldihydrosphingosine with a minor amount of stearoyldihydrosphingosine. The glycan constituent of the glycosylphosphatidylinositol-anchor was analysed by nitrous acid deamination of the aqueous phase of the PI-PLC treatment, followed by reduction with NaBH4 and hydrolysis of the phosphodiester with aqueous hydrofluoric acid. A major oligosaccharide was obtained and enzymatic treatment with exoglycosidases and further chromatography in a high pH anion exchange system showed that the trimannosyl core backbone is substituted by an alpha-galactose. A comparison between the lipid constituent of the glycosylphosphatidylinositol anchor of several proteins and their spontaneous shedding by the action of an endogenous PI-PLC was made.

The trans-sialidase of Trypanosoma cruzi is anchored by two different lipids.

The trans-sialidase from the trypomastigote stage of Trypanosoma cruzi was metabolically labeled with [3H]-palmitic acid and purified by immunoprecipitation with a monoclonal antibody. The action of PI-PLC on the immunoprecipitate released a lipid that was analyzed by TLC. Lyso-1-O-hexadecylglycerol and N-palmitoyl-sphinganine were obtained in a 1:3 ratio. A comparison with the GPI anchors present in the different stages of T. cruzi was made.

Trypanosoma cruzi: incorporation of [3H]-palmitic acid and [3H]-galactose into components shed by trypomastigotes.

Trypomastigotes were metabolically labeled with [3H]-palmitic acid or [3H]-galactose and labeled components were detected in the culture medium. Thin layer chromatography of the shed material showed several lipids in the [3H]-palmitic acid labeled sample while the sugar was mainly incorporated into macromolecules. The material incorporated with the lipidic precursor was fractionated by DEAE-Sephadex (acetate form) and the amount of radioactivity was ten times higher in the acidic lipids than in the neutral lipids. When acidic lipids were further separated by Unisil, 73% of the radioactivity was recovered in the less polar fraction. Different patterns were obtained on comparison of the shed components with the lipids remaining in the parasite.