Project description:The description of Massilia timonae, a nonfermentative aerobic gram-negative rod, was based on a single strain. A subsequent report of a second isolate has been recently published. Phenotypic descriptions of these two strains were based primarily on commercial test kit results. We have identified three additional strains as M. timonae by 16S rRNA sequence analysis and have characterized them phenotypically in parallel with the type strain of M. timonae, CIP 105350, by conventional test methods. A fourth strain, designated M. timonae-like, was also characterized. All four strains were isolated from human patients: two were blood isolates, one was isolated from cerebrospinal fluid, and one was isolated from bone. The four strains and the type strain were quite similar phenotypically. However, in contrast to the original description, the strains were found to be oxidase positive and arginine dihydrolase negative and to have lateral flagella as well as a single polar flagellum. Additionally the strains produced acid oxidatively from some carbohydrates. Other phenotypic characteristics, including cellular fatty acids, agreed with the original description. Based on our emended description, M. timonae and M. timonae-like strains can be differentiated from other aerobic nonfermentative gram-negative rods by conventional biochemical tests combined with cellular fatty acid analysis.
Project description:This work reports the amy1 gene cloning from Massilia timonae CTI-57, and its successful expression in Escherichia coli Rosetta™ (DE3) from the pTRCHis2B plasmid. The recombinant AMY1 protein had 47 kDa, and its modeled structure showed a monomer composed of three domains. An N-terminal domain with the characteristic (β/α)8-barrel structure of α-amylases, which contained the catalytic amino acid residues. The second domain was small, and the C-terminal domain was similar to those found in the barley α-amylase. A phylogenetic analysis demonstrated a high sequence identity of the studied protein with bacterial and plant α-amylases from the GH13_6 subfamily. This is the first characterized bacterial α-amylase from this glucoside hydrolase subfamily. Besides starch, the enzyme was also active against maltodextrin, amylopectin, and blocked p-nitrophenyl α-d-maltoheptaoside, but could not use β-cyclodextrin or 4-nitrophenyl α-d-glucopyranoside. The K M for highly pure grade soluble starch from potato and V max values were 0.79 mg/mL and 0.04 mg/min, respectively. The calcium ion showed to be essential for the purified enzyme's activity, while EDTA, molybdenum, cobalt, and mercury were strong inhibitors. The enzyme was almost fully active in SDS presence. The enzyme's optimal pH and temperature were 6.0 and 60 °C, respectively, and its denaturation T m was 79 °C. A TLC analysis revealed that glucose and maltose are products of the enzyme's action on starch. In conclusion, this work described the M. timonae GH13_6 subfamily α-amylase, which showed to be thermostable and anionic detergent-resistant.
Project description:We report a case of apparent malaria infection presented with a syndrome of painless, generalized lymphadenopathy without granulomas shortly after exposure to fresh water in rural West Africa. Residual infection with Massilia timonae was diagnosed and successfully treated with co-trimoxazole.