Bacteria involved in sulfur amendment oxidation and acidification processes of alkaline ‘alperujo’ compost

Eight strains of sulfur oxidizing bacteria were isolated from alkaline ‘alperujo’ compost, seven being identified as Paracoccus thiocyanatus and one as Halothiobacillus neapolitanus. This was the first time that P. thiocyanatus was isolated from mature compost. Acidification capability of isolated strains was compared with type strains H. neapolitanus CIP104769, Thiobacillus denitrificans CIP104767 and Thiomonas intermedia CIP104401. Indigenous P. thiocyanatus strains were as much as or more efficient for acidifying compost than type strains. Sulfur oxidizing population naturally occurring in compost showed maximum acidification efficiency and no extra effect was found with the help of type strains. pH reduction caused by S○ was paralleled by a decrease in CaCO3 and an increase in CaSO4 and salinity levels. A remarkable increase in cultivable sulfur oxidizing bacteria population along with the acidification process was also recorded. Amended compost showed a range of chemical and biological characteristics suitable for use as container media constituent.