[Show abstract][Hide abstract] ABSTRACT: One strain of Antarctic bacteria, Flavobacterium xanthum IAM12026, has a highly active antifreeze protein (AFP) in the intracellular space. The cell-free extract from strain IAM12026 after culturing at 4 degree C for 7 days in TSB medium, had activity of 0.04 degree C at a concentration of 0.7 mg/ml. The ice crystals formed do not have distinct facets without typically rounded shape and the changes of their morphology during the course of the thermal hysteresis (TH) measurement. The ice crystal 'burst' occurring at the end-point of the TH is dendritic with hexagonal symmetry. Also, this activity was not affected by the treatment of dialysis and the addition of EDTA. Furthermore, this cell-free extract had high levels of ice recrystallization-inhibiting (RI) activity like those of Fish AFPs. The AFP (FlAFP) was homogeneity purified using chromatography. A relative molecular mass of approximately 59,000 was calculated from gel filtration and SDS-PAGE data. The thermal stability of FlAFP was below 50 degree C, and TH value was absent above 60 degree C. The TH value of FlAFP was activated at 5.2 degree C by the addition of 0.5 M malate. This activation was decreased with increasing protein concentration. To our knowledge this is the first report on the high level of TH and RI activities of bacterial intracellular AFP.
[Show abstract][Hide abstract] ABSTRACT: The Arctic plant growth-promoting rhizobacterium Pseudomonas putida GR12-2 secretes an antifreeze protein (AFP) that promotes survival at subzero temperatures. The AFP is unusual in that it also exhibits a low level of ice nucleation activity. A DNA fragment with an open reading frame encoding 473 amino acids was cloned by PCR and inverse PCR using primers designed from partial amino acid sequences of the isolated AFP. The predicted gene product, AfpA, had a molecular mass of 47.3 kDa, a pI of 3.51, and no previously known function. Although AfpA is a secreted protein, it lacked an N-terminal signal peptide and was shown by sequence analysis to have two possible secretion systems: a hemolysin-like, calcium-binding secretion domain and a type V autotransporter domain found in gram-negative bacteria. Expression of afpA in Escherichia coli yielded an intracellular 72-kDa protein modified with both sugars and lipids that exhibited lower levels of antifreeze and ice nucleation activities than the native protein. The 164-kDa AFP previously purified from P. putida GR12-2 was a lipoglycoprotein, and the carbohydrate was required for ice nucleation activity. Therefore, the recombinant protein may not have been properly posttranslationally modified. The AfpA sequence was most similar to cell wall-associated proteins and less similar to ice nucleation proteins (INPs). Hydropathy plots revealed that the amino acid sequence of AfpA was more hydrophobic than those of the INPs in the domain that forms the ice template, thus suggesting that AFPs and INPs interact differently with ice. To our knowledge, this is the first gene encoding a protein with both antifreeze and ice nucleation activities to be isolated and characterized.
Journal of Bacteriology 10/2004; 186(17):5661-71. DOI:10.1128/JB.186.17.5661-5671.2004 · 2.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The ice-nucleating bacterium, Pantoea agglomerans NBRC12686 responds to a decrease in temperature with the induction of proteins, which are classified as cold-induced proteins. When the temperature of the strain NBRC12686 culture was lowered from 30 degree C to 12 degree C, the viability after freezing treatment significantly improved. By the use of SDS-polyacrylamide gel electrophoresis and high-performance liquid chromatography (HPLC), we analyzed the cold acclimation response in strain NBRC12686. After a shift from 30 degree C to 12 degree C, several proteins and saccharides were synthesized. After 48 h of cold acclimation, the induction level of proteins increased. In addition, ribose-1-phosphate was fractionated by HPLC using a TSK gel Sugar AXG column. Cell-free extracts were prepared from a cold acclimation culture (30 degree C to 12 degree C) and a non-cold acclimation culture (30 degree C), and then subjected to SDS-PAGE. A protein of approximately 29.7-kDa was present in the cold acclimation culture but was not present in the non-cold acclimation culture. The 29.7-kDa protein was purified by various chromatographies. We found that apparent molecular mass of the protein was approximately 119-kD constructed of 4 subunits of 29.7-kDa each. Based on the analysis of the N-terminal amino acid sequences of proteins, the 29.7-kDa protein had 83 percent identity with that of uridine phosphorylase (UPase) obtained from Escherichia coli K-12. We confirmed that the 29.7-kDa protein was novel, judged by molecular mass different from the already-known UPase or cryoprotectants. The cryoprotective activity of UPase of 29.7-kDa protein for LDH was approximately 30 percent at 5.0 microgram per ml of the protein. Furthermore, UPase had a high level of cryoprotective activity even after treating at 70 degree C for 30 min, but had no activity after treating at 100 degree C. We could elucidate that UPase from strain NBRC12686 had a cryoprotective activity as well as an enzyme activity, and it seems that UPase works in two different mechanisms for freezing tolerance.
[Show abstract][Hide abstract] ABSTRACT: Pseudomonas fluorescens KUAF-68, which was isolated from Antarctica, had both ice-nucleating protein and antifreeze protein activities in the culture broth. We found that both proteins were separately produced based on the results of column chromatography, SDS-PAGE analysis and Southern hybridization. The activity of the ice-nucleating protein was stimulated by the addition of glycine (0.020 N%), whereas the activity of the antifreeze protein was stimulated by the addition of L-asparagine (0.025 N%). This is the first report on the production of two types of ice crystal-controlling proteins in one bacterial strain.
Journal of Bioscience and Bioengineering 02/2004; 98(3):220-3. DOI:10.1016/S1389-1723(04)00271-3 · 1.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Some ice-nucleating bacterial strains, including Pantoea ananatis (Erwinia uredovora), Pseudomonas fluorescens, and Pseudomonas syringae isolates, were examined for the ability to shed ice nuclei into the growth medium. A novel ice-nucleating bacterium, Pseudomonas antarctica IN-74, was isolated from Ross Island, Antarctica. Cell-free ice nuclei from P. antarctica IN-74 were different from the conventional cell-free ice nuclei and showed a unique characterization. Cell-free ice nuclei were purified by centrifugation, filtration (0.45 microm), ultrafiltration, and gel filtration. In an ice-nucleating medium in 1 liter of cell culture, maximum growth was obtained with the production of 1.9 mg of cell-free ice nuclei. Ice nucleation activity in these cell-free ice nuclei preparations was extremely sensitive to pH. It was demonstrated that the components of cell-free ice nuclei were protein (33%), saccharide (12%), and lipid (55%), indicating that cell-free ice nuclei were lipoglycoproteins. Also, carbohydrate and lipid stains showed that cell-free ice nuclei contained both carbohydrate and lipid moieties.
[Show abstract][Hide abstract] ABSTRACT: An ice-nucleating protein (INP) from the extracellular ice-nucleating matter (EIM) of Pantoea ananatis (Erwinia uredovora) KUIN-3 was purified and characterized. The EIM produced by the strain KUIN-3 was purified by ultrafiltration, sucrose density-gradient ultracentrifugation and gel filtration. The INP was purified using of column chromatography on hydroxyapatite and Superdex 200 in the nondenaturing detergent of 0.1% (w/v) Triton X-100. The purified INP was composed of one subunit of 117 kDa according to SDS-PAGE. It has become apparent that the INP was the ice-nucleating lipoglycoprotein based on the reaction of carbohydrate stain and lipid stain with the INP. It was inhibited by p-mercuribenzoate and N-bromosuccinimide. The activity of the INP gradually decreased from 65 degrees C. The pH stability was held between pH 7.0 and pH 11.0. The INP had a lower ice-nucleating temperature below pH 6.0. It has become apparent that the INP consisted of the class C structure in the EIM based on its freezing difference spectrum in D2O versus H2O.
Journal of Bioscience and Bioengineering 02/2003; 95(2):157-63. DOI:10.1263/jbb.95.157 · 1.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A novel ice-nucleating bacterium (INB) was isolated from Ross Island, Antarctica. INBs could be isolated more frequently than was generally thought. INB strain IN-74 was found in the white colony group. Strain IN-74 was identified from its taxonomic characteristics as a novel INB, Pseudomonas antarctica IN-74. When strain IN-74 was cultured aerobically in a medium consisting of the ice-nucleating broth (pH 7.0) for 6 days at 4 degrees C, the ice-nucleating activity of strain IN-74 cells was obtained. Strain IN-74 cells produced ice nuclei only at extremely low growth temperatures. The nuclei appeared to be less thermolabile than those of INB Pseudomonas fluorescens KUIN-1. The freezing difference spectra in D2O and H2O at ice-nucleating temperature for strain IN-74 cells and conventional INBs (Pseudomonas fluorescens KUIN-1, Pseudomonas viridiflava KUIN-2, and Pseudomonas syringae C-9) exhibited different curves.