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| Author(s): |
Adriano Reis Lucheta
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2011-02-18 |
| Examining board members: |
Marcio Rodrigues Lambais;
Fernando Dini Andreote;
Denise Bevilaqua;
Itamar Soares de Melo;
Luis Ignacio Prochnow
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| Advisor: | Marcio Rodrigues Lambais |
| Abstract | |
Depletion of sulfur levels in soil has been observed as a result of agricultural practices and biomass harvesting. Elemental sulfur (S0) may be an interesting fertilizer, however it must be oxidized to sulfate in order to be taken up by plants. Biological oxidation of S0 is commonly associated to Acidithiobacillus thiooxidans, although many studies failed to detect them in soils. Recent efforts have shown a great diversity of microorganisms able to oxidize S0, besides A. thiooxidans. Nevertheless, no information is available for Brazilian soils. The aims of this work were to determine the S0 oxidation rates of three Brazilian soils, the bacterial and archaeal communities diversity associated to S0 oxidation, as well as, to isolate sulfur oxidizing bacteria (SOB) and evaluate its potential as a biofertilizer. Soils sampled in Anhembi, SP (ANB), Brasília, DF (BRA) and Rondonópolis, MT (RDP) were enriched with 10 g of S0 kg-1 (+S0) or not (-S0) and incubated in microcosms for 0, 6, 22, 38, 54, 67, 86 and 102 days under 28 oC. Oxidation rates of S0 were low, ranging to 2,8 and 3,2 ug S cm-2 day-2 in the sand soils (RDP and BRA) and 1,3 ug S cm-2 day-2 in the clay one (BRA) after 102 days incubation. Soil SO4 2- content was increased and pH decreased as result of S0 oxidation mainly in the sand soils. Bacterial community structure and diversity were affected by S0 amendment and time of incubation, represented by changes in the DGGE profile and phylum distribution. Were obtained 811 bacterial 16S rRNA sequences, clustered in 518 Operational Taxonomic Units (OTUs). The predominant phyla in the soils were Acidobacteria, Actinobacteria, Firmicutes and Proteobacteria. Were obtained 463 archaeal 16S rRNA sequences clustered into 39 OTUs. More than 84% of the OTUs were assembled to unclassified Archaea whereas 15% were classified as Euryarchaeota. Archaea diversity was not mostly affected by S0. Fifty SOB were isolated and affiliated to Proteobacteria (68%), Actinobacteria (18%) and Firmicutes (14%) after 16S rRNA sequencing. The assigned genera were Aurantimonas, Acinetobacter, Novosphingobium, Methylobacterium, Paracoccus, Bradyrhizobium, Sphingomonas, Mycobacterium, Micrococcus and Bacillus. Alginate beads containing the SOB isolates ANB9 (Acinetobacter), RDP5 (Mycobacterium) and A. thiooxidans plus S0 were incubated in sterile sand resulting in 111%, 430% and 5350% increment in SO4 2- comparing to negative controls after 14 days incubation, respectively. The S0 oxidation rate was 4,7 (ANB9), 18 (RDP5) and 130 (A. thiooxidans) times greater than the negative control after the same time. The entrapped bacteria with S0 were incubated in ANB and BRA soils for 54 days in microcosms. A. thiooxidans was the best S0 oxidizer, showing the highest oxidation rate, increment in SO4 2- and pH decrease comparing with the other SOB isolates. A. thiooxidans beads were also able to solubilize phosphate rock. New information was generated about the bacterial diversity involved in the S0 oxidation in Brazilian soils. (AU) | |
| FAPESP's process: | 07/06957-4 - Microbiological oxidation of elemental sulfur in soil |
| Grantee: | Adriano Reis Lucheta |
| Support Opportunities: | Scholarships in Brazil - Doctorate |