RESUMO
Serratia marcescens WW4 is a biofilm-forming bacterium isolated from paper machine aggregates. Under conditions of phosphate limitation, this bacterium exhibits intergeneric inhibition of Pseudomonas aeruginosa. Here, the complete genome sequence of S. marcescens WW4, which consists of one circular chromosome (5,241,455 bp) and one plasmid (pSmWW4; 3,248 bp), was determined.
RESUMO
Phosphate is an essential nutrient for heterotrophic bacteria, affecting bacterioplankton in aquatic ecosystems and bacteria in biofilms. However, the influence of phosphate limitation on bacterial competition and biofilm development in multispecies populations has received limited attention in existing studies. To address this issue, we isolated 13 adhesive bacteria from paper machine aggregates. Intergeneric inhibition of Pseudomonas aeruginosa WW5 by Serratia marcescens WW4 was identified under phosphate-limited conditions, but not in Luria-Bertani medium or M9 minimal medium. The viable numbers of the pure S. marcescens WW4 culture decreased over 3 days in the phosphate-limited medium; however, the mortality of S. marcescens WW4 was significantly reduced when it was co-cultured with P. aeruginosa WW5, which appeared to sustain the S. marcescens WW4 biofilm. In contrast, viable P. aeruginosa WW5 cells immediately declined in the phosphate-limited co-culture. To identify the genetic/inhibitory element(s) involved in this process, we inserted a mini-Tn5 mutant of S. marcescens WW4 that lacked inhibitory effect. The results showed that an endonuclease bacteriocin was involved in this intergeneric inhibition by S. marcescens WW4 under phosphate limitation. In conclusion, this study highlights the importance of nutrient limitation in bacterial interactions and provides a strong candidate gene for future functional characterisation.
Assuntos
Biofilmes/crescimento & desenvolvimento , Interações Microbianas , Fosfatos/farmacologia , Pseudomonas aeruginosa/fisiologia , Serratia marcescens/fisiologia , Antibiose , Aderência Bacteriana , Bacteriocinas/metabolismo , Biofilmes/efeitos dos fármacos , Meios de Cultura , Elementos de DNA Transponíveis , Viabilidade Microbiana , Mutagênese Insercional , Papel , Pseudomonas aeruginosa/efeitos dos fármacos , Pseudomonas aeruginosa/isolamento & purificação , Serratia marcescens/efeitos dos fármacos , Serratia marcescens/genética , Serratia marcescens/isolamento & purificaçãoRESUMO
The Cel-BL11 gene from Paenibacillus campinasensis BL11 was cloned and expressed in Escherichia coli as a His-tag fusion protein. Zymographic analysis of the recombinant protein revealed cellulase activity corresponding to a protein with a 38-kDa molecular weight. The optimum temperature and pH for purified cellulase were 60 °C and pH 7.0, respectively. The enzyme retained more than 80% activity after 8h at 60 °C at pH 6 and 7. The cellulase has a Km of 11.25 mg/ml and a Vmax of 1250 µmol/min/mg with carboxylmethyl cellulose (CMC). Then enzyme was active on Avicel, swollen Avicel, CMC, barley ß-glucan, laminarin in the presence of 100 mM acetate buffer. It was inhibited by Hg²âº, Cu²âº and Zn²âº. Significant kraft pulp refining energy saving, 10%, was exhibited by the pretreatment of this cellulase applied at 2 IU per gram of oven-dried pulp. Broad pH and temperature stability render this cellulase a convenient applicability toward current mainstream biomass conversion and other industrial processes.
Assuntos
Celulase/metabolismo , Escherichia coli/genética , Paenibacillus/enzimologia , Sequência de Bases , Celobiose/metabolismo , Celulase/genética , Clonagem Molecular , Primers do DNA , Estabilidade Enzimática , Concentração de Íons de Hidrogênio , Hidrólise , Cinética , Reação em Cadeia da Polimerase , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Especificidade por Substrato , TemperaturaRESUMO
In order to search for new thermophilic microorganisms and their enzymes, bacterial strains from black liquor of brownstock at washing stage of kraft pulping process were screened. Therein a multiple glycosyl hydrolase-producing strain, BL11, was isolated as a dominant species in the xylan-degrading bacterial population and identified as Paenibacillus campinasensis. The bacterial strain used all kinds of saccharides and polysaccharides, except lignin as carbon source and produced multiple extracellular polysaccharide-degrading enzymes, including one xylanase (41 kDa), three cellulases (42, 57 and 86 kDa), one pectinase (28 kDa) and one cyclodextrin glucanotransferase (38 kDa). P. campinasensis BL11 lacked lipase and protease activities and was able to grow over a wide range of pH, but it particularly grew well around neutral pH at 55 degrees C. Based on its physiological characteristics, it has strong potential for industrial application and bioresource utilization.
Assuntos
Bacillaceae/isolamento & purificação , Resíduos Industriais , Polissacarídeos/metabolismo , Bacillaceae/enzimologia , Bacillaceae/metabolismo , Celulases/metabolismo , Glicosídeo Hidrolases/metabolismo , Temperatura Alta , Concentração de Íons de Hidrogênio , Filogenia , Madeira/metabolismo , Xilanos/metabolismoRESUMO
A Ca(2+)/calmodulin-dependent protein kinase (CaMK) gene was cloned and characterized from Arthrobotrys dactyloides, a nematode-trapping fungus. The resulting 373-amino-acid protein, FCaMK, has significant homology to mammalian CaMKs. FCaMK contains a serine/threonine kinase domain followed by a calmodulin-binding domain. The activation loop in FCaMK (amino acids 184-199) contains a phosphorylation site at threonine-188, which could be the target of a kinase activator. Truncated FCaMK mutants revealed that amino acids 296-324 are essential for calmodulin binding. An oligopeptide designed from residues 297-324 formed a stable peptide-calmodulin complex of 1:1 stoichiometry. Southern blot analysis detected a single copy of the fcamk gene, suggesting that FCaMK plays an important role in Ca(2+)/calmodulin signaling in A. dactyloides.