RESUMO
Lactobacillus bulgaricus is commonly used in dairy products as a starter culture. Its viability during freeze-drying is of commercial interest. Here a significant (p < 0.05) improvement in survival rate of L. bulgaricus ATCC 11842 was achieved during freeze-drying when it was prestressed with 2 % (w/v) NaCl for 2 h in the late growth phase. To understand the mechanism of this stress-related viability improvement in L. bulgaricus, protein synthesis was analyzed by 2D difference gel electrophoresis. Nine protein spots were significantly altered by NaCl and were subsequently identified by peptide mass fingerprinting. The functions of the proteins included stress-related protein synthesis, amino acid biosynthesis, nucleotide biosynthesis, sugar metabolism, transport systems, and vitamin biosynthesis. These findings provide a considerable background regarding the NaCl stress response of L. bulgaricus.
Assuntos
Proteínas de Bactérias/análise , Lactobacillus/efeitos dos fármacos , Proteoma/efeitos dos fármacos , Proteômica/métodos , Cloreto de Sódio/toxicidade , Estresse Fisiológico/efeitos dos fármacos , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Eletroforese em Gel Bidimensional , Liofilização , Lactobacillus/metabolismo , Proteoma/análise , Proteoma/química , Proteoma/metabolismo , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por MatrizRESUMO
The water environment capacity of urban parks is small, and their self-purification ability is poor. They are also more likely to be affected by microplastics (MPs), which cause an imbalance of the water micro-ecosystem. Based on the functional characteristics of parks (comprehensive park, community park, and ecological park), this study investigated the distribution characteristics of MPs in the water of Guilin parks through spot sampling, microscopic observation, and Fourier transform infrared spectroscopy. In addition, the pollution risk index and the pollution load index were used to evaluate the pollution risk of MPs.The results showed that the abundances of MPs in the park surface water and sediments ranged from 104.67-674.44 n·m-3 and 95.57-877.78 n·kg-1, respectively. There were four main shape types of MPs:fragments, fibers, films, and particles. MPs were dominated by fragments and fibers with small sizes (<1 mm). The polymers of MPs were polyethylene and polyethylene terephthalate. There were significant differences in the abundance of MPs in the water of different functional parks, and the abundance of MPs in comprehensive parks was the highest. The abundance of MPs in park water was closely related to the function of the park and the number of people entering the park. The pollution risk of MPs in the surface water of Guilin parks was low, whereas the pollution risk of MPs in sediments was relatively high. The results of this study indicated that tourism was an important source of MPs pollution in the water of Guilin City parks. The pollution risk of MPs in the water of Guilin City parks was mild. However, the pollution risk of MPs accumulated in small freshwater waters of urban parks requires continued attention.