Identification and characterization of two types of amino acid-regulated acetyltransferases in actinobacteria.

One hundred and fifty GCN5-like acetyltransferases with amino acid-binding (ACT)-GCN5-related N-acetyltransferase (GNAT) domain organization have been identified in actinobacteria. The ACT domain is fused to the GNAT domain, conferring amino acid-induced allosteric regulation to these protein acetyltransferases (Pat) (amino acid sensing acetyltransferase, (AAPatA)). Members of the AAPatA family share similar secondary structure and are divided into two groups based on the allosteric ligands of the ACT domain: the asparagine (Asn)-activated PatA and the cysteine (Cys)-activated PatA. The former are mainly found in Streptomyces; the latter are distributed in other actinobacteria. We investigated the effect of Asn and Cys on the acetylation activity of Sven_0867 (SvePatA, from Streptomyces venezuelae DSM 40230) and Amir_5672 (AmiPatA, from Actinosynnema mirum strain DSM 43827), respectively, as well as the relationship between the structure and function of these enzymes. These findings indicate that the activity of PatA and acetylation level of proteins may be closely correlated with intracellular concentrations of Asn and Cys in actinobacteria. Amino acid-sensing signal transduction in acetyltransferases may be a mechanism that regulates protein acetylation in response to nutrient availability. Future work examining the relationship between protein acetylation and amino acid metabolism will broaden our understanding of post-translational modifications (PTMs) in feedback regulation.

[Efficiency of Aerobic Co-composting of Urban Sludge and Chinese Medicinal Herbal Residues].

With Chinese medicinal herbal residues and municipal sludge as raw materials for co-composting experiment, the effect of the material ratio and addition time of Chinese medicinal herbal residues on the composting efficiency were investigated, including the change of the temperature, organic matter, ammonia nitrogen, and activity of protease. The best composting conditions were determined based on the results. The experimental results showed that the temperature of the pile was raised in the presence of 60 g Chinese medicinal herbal residues as carbon source and 300 g municipal sludge, the ammonia volatilization was reduced and the activity of protease was improved. The ammonia volatilization was reduced by 35.9% and the activity of protease was increased by 80.5% in 15 d, respectively. Especially, in the early stage, addition of Chinese medicinal herbal residues as conditioner could increase the organic matter degradation. Thus, the composting process was accelerated. Changes in the UV-visible and fluorescence characteristics of dissolved organic matter (DOM) during the co-composting process were discussed. The treatment with Chinese medicinal herbal residues improved the maturity of the compost. Moreover, phospholipid fatty acid (PLFA) method was used to estimate the microbial community structure changes. It showed that the number of microbial community such as fungi and Gram negative bacteria increased with addition of Chinese medicinal herbal residues.