Aeromonas proteolytica--a halophilic aeromonad?

Aeromonas proteolytica, a halophilic bacterium originally isolated from the intestine of a marine isopod, was compared with 93 strains of Aeromonas hydrophila and representative strains of five similar genera in a computer and serological analysis. Aeromonas proteolytica was peritrichate and non-reactive with six A. hydrohila antisera, and possessed a percentage guanine + cytosine ratio (49.5) outside the range for other aeromonads (55-62%). Moreover, in the computer analysis it shared a lower level of similarity with other aeromonads than with both strains of Vibrio anguillarum tested.     

β-Lactamases from Actinopolyspora halophila,an extremely halophilic actinomycete

Actinopolyspora halophila, an extremely halophilic actinomycete, produced both cellular and exocellular -lactamases when grown in liquid media containing 20% (w/v) NaCl. Maximal exocellular -lactamase production occurred at 48 h growth and exceeded cellular enzyme levels 7-fold. Maximal cellular -lactamase was observed at 72 h as cultures achieved full growth.Both -lactamases were purified to molecular homogeneity by a sequence involving gel filtration on Bio-Gel P-100, DEAE Bio-Gel A chromatography, preparative isoelectric focusing, and gel filtration on Sephadex G-75. Cellular -lactamase was purified 99-fold with 12% recovery and had a molecular weight of 42,200, and an isoelectric point of 4.15. Exocellular -lactamase was 12-fold purified with 1.2% recovery of initial activity and had a molecular weight of 38,000 and an isoelectric point of 3.85. Its specific activity was 7-fold greater than that of the cellular enzyme.A variety of penicillin and cephalosporin substrates were degraded by both enzymes. While the cellular -lactamase degraded phenoxymethylpenicillin, methicillin, and cephaloglycin most efficiently, the exocellular enzyme was most active against methicillin, carbenicillin, ampicillin, and cephalosporin C. Both enzymes were stimulated and protected from thermal deactivation by NaCl but not KCl or MgCl₂-Neither enzyme was inhibited by iodine.Abbreviations IEF Isoelectric focusing - SDS-PAGE sodium dodecylsulphate-polyacrylamide electrophoresis - PEG polyethyleneglycol - DTT dithiothreitol - DEAE diethylaminoethyl Issued as NRCC 25164     

Purification and characterization of a halophilic α-amylase with increased activity in the presence of organic solvents from the moderately halophilic Nesterenkonia sp. strain F

An extracellular halophilic α-amylase was purified from Nesterenkonia sp. strain F using 80 % ethanol precipitation and Q-Sepharose anion exchange chromatography. The enzyme showed a single band with an apparent molecular weight of 110 kDa by SDS-PAGE. The amylase exhibited maximal activity at pH 7-7.5, being relatively stable at pH 6.5-7.5. Optimal temperature for the amylase activity and stability was 45 °C. The purified enzyme was highly active in the broad range of NaCl concentrations (0-4 M) with optimal activity at 0.25 M NaCl. The amylase was highly stable in the presence of 3-4 M NaCl. Amylase activity was not influenced by Ca2?, Rb?, Li?, Cs?, Mg2? and Hg2?, whereas Fe3?, Cu2?, Zn2? and Al3?) strongly inhibited the enzyme activity. The α-amylase was inhibited by EDTA, but was not inhibited by PMSF and β-mercaptoethanol. K(m) value of the amylase for soluble starch was 6.6 mg/ml. Amylolytic activity of the enzyme was enhanced not only by 20 % of water-immiscible organic solvents but also by acetone, ethanol and chloroform. Higher concentration (50 %) of the water-miscible organic solvents had no significant effect on the amylase activity. To the best of our knowledge, this is the first report on increased activity of a microbial α-amylase in the presence of organic solvents.     

Characterisation of a highly stable α-amylase from the halophilic archaeon Haloarcula hispanica

Intracellular and extracellular proteins from halophilic archaea face very saline conditions and must be able to maintain stability and functionality at nearly saturated salt concentrations. Haloarchaeal proteins contain specific adaptations to prevent aggregation and loss of activity in such conditions, but these adaptations usually result in a lack of stability in the absence of salt. Here, we present the characterisation of a secreted -amylase (AmyH) from the halophilic archaeon Haloarcula hispanica. AmyH was shown to be very halophilic but, unusually for a halophilic protein, it retained activity in the absence of salt. Intrinsic fluorescence measurements and activity assays showed that AmyH was very stable in high-salt buffer and even maintained stability upon the addition of urea. Urea-induced denaturation was only achieved in the absence of NaCl, demonstrating clearly that the stability of the protein was salt-dependent. Sequencing of the amyH gene showed an amino acid composition typical of halophilic proteins and, moreover, the presence of a signal peptide containing diagnostic features characteristic of export via the Twin-arginine translocase (Tat). Analysis of the export of AmyH showed that it was translocated post-translationally, most likely in a folded and active conformation, confirming that AmyH is a substrate of the Tat pathway.     

Purification and characterization of an organic-solvent-tolerant halophilic α-amylase from the moderately halophilic <Emphasis Type="Italic">Nesterenkonia</Emphasis> sp. strain F

A halophilic α-amylase produced by Nesterenkonia sp. strain F was purified to homogeneity by 80% ethanol precipitation, Q-Sepharose anion exchange, and Sephacryl S-200 gel filtration chromatography. The purified amylase exhibited specific activity of 357 unit/mg protein that corresponds to twofold purification. The molecular mass of the amylase was determined to be 57 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and gel filtration chromatography. The optimal pH and temperature for enzyme activity were 6.5 and 45°C, respectively. The amylase was active over a wide range of salt concentrations (0–4 M) with maximum activity at 0.75–1 M NaCl. The α-amylase activity was stimulated by Ca²⁺ and inhibited by ethylenediamine tetraacetic acid (EDTA), suggesting that this enzyme is a metalloenzyme. The purified enzyme showed remarkable stability towards surfactants (Tween 20, Tween 80, and Triton X-100), and its activity was increased by β-mercaptoethanol. The halophilic α-amylase was stable in the presence of various organic solvents such as benzene, chloroform, toluene, and cyclohexane. These properties indicate wide potential applications of this α-amylase in starch-processing industries.     

Purification and biochemical characterization of a novel SDS and surfactant stable,raw starch digesting,and halophilic α-amylase from a moderately halophilic bacterium,Nesterenkonia sp. strain F

An extracellular halophilic α-amylase from Nesterenkonia sp. strain F was purified to homogeneity by 80% ethanol precipitation, Q-Sepharose anion exchange and Sephacryl S-200 gel filtration chromatography, with a 10.8-fold increase in specific activity. The molecular mass of the amylase was estimated to be 100 kDa and 106 kDa by SDS–PAGE and gel filtration chromatography, respectively. The enzyme showed maximal activity at pH 7.5 and 45 °C. The amylase was active in a wide range of salt concentrations (0–4 M) with its maximum activity at 0.5 M NaCl or 1 M KCl and was stable at the salts concentrations between 1 M and 4 M. Fe³⁺, Cu²⁺, Zn²⁺ and Al³⁺ strongly inhibited the enzyme, whereas Ca²⁺ stimulated the amylase activity. The α-amylase was inhibited by EDTA, but was not inhibited by PMSF and β-mercaptoethanol. The enzyme showed remarkable stability towards 0.5% SDS and sarcosyl, and 2% each of Triton X-100, Tween 80 and Tween 20. K_m value of the amylase for soluble starch was 4.5 mg/ml. The amylase hydrolyzed 38% of raw wheat starch and 20% of corn starch in a period of 48 h. The major products of soluble starch hydrolysis were maltose, maltotriose and maltotetraose, indicating an α-amylase activity.     

Biochemical characterization of an extracellular polyextremophilic α-amylase from the halophilic archaeon Halorubrum xinjiangense

An extracellular haloalkaliphilic thermostable α-amylase producing archaeon was isolated from the saltwater Lake Urmia and identified as Halorubrum xinjiangense on the basis of morphological, biochemical, and molecular properties. The enzyme was purified to an electrophoretically homogenous state by 80 % cold ethanol precipitation, followed by affinity chromatography. The concentrated pure amylase was eluted as a single peak on fast protein liquid chromatography. The molecular mass of the purified enzyme was about 60 kDa, with a pI value of 4.5. Maximum amylase activity was at 4 M NaCl or 4.5 M KCl, 70 °C, and pH 8.5. The K _m and V _max of the enzyme were determined as 3.8 mg ml^?1 and 12.4 U mg^?1, respectively. The pure amylase was stable in the presence of SDS, detergents, and organic solvents. In addition, the enzyme (20 U) hydrolyzed 69 % of the wheat starch after a 2-h incubation at 70 °C in an aqueous/hexadecane two-phase system.     

Identification of N δ-acetylornithine as a novel osmolyte in some Gram-positive halophilic eubacteria

In the course of a screening programme for novel natural substances acting as compatible solutes, an unusual amino acid derivative was detected in several halophilic Gram-positive eubacteria. The compound was isolated and subsequently identified as N -acetylornithine using spectroscopic (NMR, MS) and chromatographic methods. So far, N -acetylornithine has only been described as an excretion product of some bacteria under certain growth conditions. This report describes, for the first time, its intracellular accumulation and use as a compatible solute in halophilic/halotolerant eubacteria. Correspondence to: E. A. Galinski     

Salt-dependent thermo-reversible α-amylase: cloning and characterization of halophilic α-amylase from moderately halophilic bacterium, <Emphasis Type="Italic">Kocuria varians</Emphasis>

A moderately halophilic bacterium, Kocuria varians, was found to produce active α-amylase (K. varians α-amylase (KVA)). We have observed at least six different forms of α-amylase secreted by this bacterium into the culture medium. Characterization of these KVA forms and cloning of the corresponding gene revealed that KVA comprises pre-pro-precursor form of α-amylase catalytic domain followed by the tandem repeats, which show high similarity to each other and to the starch binding domain (SBD) of other α-amylases. The observed six forms were most likely derived by various processing of the protein product. Recombinant KVA protein was successfully expressed in Escherichia coli as a fusion protein and was purified with affinity chromatography after cleavage from fusion partner. The highly acidic amino acid composition of KVA and the highly negative electrostatic potential surface map of the modeled structure strongly suggested its halophilic nature. Indeed, KVA showed distinct salt- and time-dependent thermal reversibility: when α-amylase was heat denatured at 85°C for 3 min in the presence of 2 M NaCl, the activity was recovered upon incubation on ice (50% recovery after 15 min incubation). Conversely, KVA denatured in 0.1 M NaCl was not refolded at all, even after prolonged incubation. KVA activity was inhibited by proteinaceous α-amylase inhibitor from Streptomyces nitrosporeus, which had been implicated to inhibit only animal α-amylases. KVA with putative SBD regions was found to digest raw starch.     

A new GH13 subfamily represented by the α-amylase from the halophilic archaeon Haloarcula hispanica

Extremophiles - α-Amylase catalyzes the endohydrolysis of α-1,4-glucosidic linkages in starch and related α-glucans. In the CAZy database, most α-amylases have been classified...     

The Na(+)-translocating F₁F₀-ATPase from the halophilic, alkalithermophile Natranaerobius thermophilus

Natranaerobius thermophilus is an unusual anaerobic extremophile, it is halophilic and alkalithermophilic; growing optimally at 3.3-3.9M Na(+), pH(50°C) 9.5 and 53°C. The ATPase of N. thermophilus was characterized at the biochemical level to ascertain its role in life under hypersaline, alkaline, thermal conditions. The partially purified enzyme (10-fold purification) displayed the typical subunit pattern for F-type ATPases, with a 5-subunit F(1) portion and 3-subunit-F(O) portion. ATP hydrolysis by the purified ATPase was stimulated almost 4-fold by low concentrations of Na(+) (5mM); hydrolysis activity was inhibited by higher Na(+) concentrations. Partially purified ATPase was alkaliphilic and thermophilic, showing maximal hydrolysis at 47°C and the alkaline pH(50°C) of 9.3. ATP hydrolysis was sensitive to the F-type ATPase inhibitor N,N'-dicylohexylcarbodiimide and exhibited inhibition by both free Mg(2+) and free ATP. ATP synthesis by inverted membrane vesicles proceeded slowly and was driven by a Na(+)-ion gradient that was sensitive to the Na(+)-ionophore monensin. Analysis of the atp operon showed the presence of the Na(+)-binding motif in the c subunit (Q(33), E(66), T(67), T(68), Y(71)), and a complete, untruncated ε subunit; suggesting that ATP hydrolysis by the enzyme is regulated. Based on these properties, the F(1)F(O)-ATPase of N. thermophilus is a Na(+)-translocating ATPase used primarily for expelling cytoplasmic Na(+) that accumulates inside cells of N. thermophilus during alkaline stress. In support of this theory are the presence of the c subunit Na(+)-binding motif and the low rates of ATP synthesis observed. The complete ε subunit is hypothesized to control excessive ATP hydrolysis and preserve intracellular Na(+) needed by electrogenic cation/proton antiporters crucial for cytoplasmic acidification in the obligately alkaliphilic N. thermophilus.     

Organic solvent tolerance of halophilic α-amylase from a Haloarchaeon, Haloarcula sp. strain S-1

A halophilic archaeon, Haloarcula sp. strain S-1, produced extracellular organic solvent-tolerant -amylase. Molecular mass of the enzyme was estimated to be 70 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This amylase exhibited maximal activity at 50°C in buffer containing 4.3 M NaCl, pH 7.0. Moreover, the enzyme was active and stable in various organic solvents (benzene, toluene, and chloroform, etc.). Activity was not detected at low ionic strengths, but it was detected in the presence of chloroform at low salt concentrations. On the other hand, no activity was detected in the presence of ethyl alcohol and acetone.     

Could halophilic archaea improve the traditional salted anchovies (Engraulis encrasicholus L.) safety and quality?

Aims: The positive influence of two selected extremely halophilic archaea strains in the production of salted anchovies (Engraulis encrasicolus, L., 1758) was highlighted. Methods and Results: Anchovies produced with salt artificially contaminated with halophiles exhibited lower loads of staphylococci, Enterobacteriaceae and lactic acid bacteria, and a reduced content of histamine as well as an improved organoleptic acceptance. Conclusions: The findings of this survey are expected to enhance the safety of salted anchovies, with regard to the histamine formation during ripening, and to improve the sensory attributes of this product. Significance and Impact of the Study: This study represents the first report on the positive influence of halophilic archaea in traditional salted anchovies production, thus suggesting new perspectives about a conscious employment of properly selected haloarchaea strains in this traditional manufacture.     

NO3 −/NO2 − assimilation in halophilic archaea: physiological analysis, nasA and nasD expressions

The haloarchaeon Haloferax mediterranei is able to assimilate nitrate or nitrite using the assimilatory nitrate pathway. An assimilatory nitrate reductase (Nas) and an assimilatory nitrite reductase (NiR) catalyze the first and second reactions, respectively. The genes involved in this process are transcribed as two messengers, one polycistronic (nasABC; nasA encodes Nas) and one monocistronic (nasD; codes for NiR). Here we report the Hfx mediterranei growth as well as the Nas and NiR activities in presence of high nitrate, nitrite and salt concentrations, using different approaches such as physiological experiments and enzymatic activities assays. The nasA and nasD expression profiles are also analysed by real-time quantitative PCR. The results presented reveal that the assimilatory nitrate/nitrite pathway in Hfx mediterranei takes place even if the salt concentration is higher than those usually present in the environments where this microorganism inhabits. This haloarchaeon grows in presence of 2 M nitrate or 50 mM nitrite, which are the highest nitrate and nitrite concentrations described from a prokaryotic microorganism. Therefore, it could be attractive for bioremediation applications in sewage plants where high salt, nitrate and nitrite concentrations are detected in wastewaters and brines.     

Identification of a halophilic α-amylase gene from Escherichia coli JM109 and characterization of the recombinant enzyme

A halophilic α-amylase (EAMY) gene from Escherichia coli JM109 was overexpressed in E. coli XL10-Gold and the recombinant protein was purified and characterized. The activity of the EAMY depended on the presence of both Na⁺ and Cl^?, and had maximum activity in 2 M NaCl at 55 °C and pH 7.0. When 2 % (w/v) soluble starch was used as substrate, the specific activity was about 1,090 U mg^?1 protein. This is the first report on identifying a halophilic α-amylase with high specific activity from non-halophilic bacteria.     

A predicted geranylgeranyl reductase reduces the ω-position isoprene of dolichol phosphate in the halophilic archaeon, Haloferax volcanii

In N-glycosylation in both Eukarya and Archaea, N-linked oligosaccharides are assembled on dolichol phosphate prior to transfer of the glycan to the protein target. However, whereas only the α-position isoprene subunit is saturated in eukaryal dolichol phosphate, both the α- and ω-position isoprene subunits are reduced in the archaeal lipid. The agents responsible for dolichol phosphate saturation remain largely unknown. The present study sought to identify dolichol phosphate reductases in the halophilic archaeon, Haloferax volcanii. Homology-based searches recognize HVO_1799 as a geranylgeranyl reductase. Mass spectrometry revealed that cells deleted of HVO_1799 fail to fully reduce the isoprene chains of H. volcanii membrane phospholipids and glycolipids. Likewise, the absence of HVO_1799 led to a loss of saturation of the ω-position isoprene subunit of C(55) and C(60) dolichol phosphate, with the effect of HVO_1799 deletion being more pronounced with C(60) dolichol phosphate than with C(55) dolichol phosphate. Glycosylation of dolichol phosphate in the deletion strain occurred preferentially on that version of the lipid saturated at both the α- and ω-position isoprene subunits.     

α-Amylase activity from the halophilic archaeon<Emphasis Type="Italic"> Haloferax mediterranei</Emphasis>

The halophilic archaeon Haloferax mediterranei is able to grow in a minimal medium containing ammonium acetate as a carbon and nitrogen source. When this medium is enriched with starch, alpha-amylase activity is excreted to the medium in low concentration. Here we report methods to concentrate and purify the enzyme. The relative molecular mass of the enzyme, determined by gel filtration, is 50 +/- 4 kDa, and on SDS-PAGE analysis a single band appeared at 58 kDa. These results indicated that the halophilic alpha-amylase is a monomeric enzyme. The enzyme showed a salt requirement for both stability and activity, being stable from 2 to 4 M NaCl, with maximal activity at 3 M NaCl. The enzyme displayed maximal activity at pHs from 7 to 8, and its optimal temperature was in a range from 50 degrees C to 60 degrees C. The results also implicated several prototropic groups in the catalytic reaction.