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A xylanase gene, xynA, which encodes xylanase I of Aeromonas caviae ME-1, was cloned in Escherichia coli. xynA gene has a 633 bp open reading frame (encoding 211 amino acid residues) which includes a signal peptide (28 amino acid residues). E. coli JM109 transformant produced 0.7 U/ml xylanase, about 80% of which was secreted into the culture medium as mature enzyme. The deduced amino acid sequence shows 79.3, 78.9, and 47.1% identity to family G xylanases of Bacillus subtilis, Bacillus pumilus and Bacillus circulans, respectively.

A non-woven fabric was successfully applied for immobilization of Candida tropicalis to produce xylitol from d-xylose. Xylitol productivity was enhanced by feeding of d-glucose (50 g/l·d); 87 g xylitol/L was produced after 64 h cultivation. Non-woven fabric could be used five times for fed-batch cultivation.

d -Glucose fed-batch cultivation was studied for effective production of xylitol from d -xylose by Candida tropicalis. When d -xylose was used as a single carbon source, the yeast consumed d -xylose for production of xylitol as well as for growth and cell maintenance resulting in decreased xylitol yield. To improve the xylitol yield, it is necessary to increase the cell mass using another carbon source. We selected d -glucose for the purpose and as a result, a 1.1–1.2 times higher yield and a 1.2–1.3 times higher production rate were obtained by supplementation of d -glucose using column reactors (200 ml scale). In a bench-scale fermentor (3 l scale) experiment, xylitol was produced at up to 104.5 g/l at 32 h cultivation and a yield of 0.82 (g/g d -xylose consumed) and production rate of 3.26 g/l·h were obtained. These values are 1.3 times and 1.2 times higher for yield and production rate, respectively, than those obtained under optimum cultivation conditions for production rate previously reported.

The mass balances of sugar and ethanol were computed on the assumption that the trickle bed bioreactor used was a continuous-flow stirred-tank reactor (CSTR), and simulation of the steady ethanol concentration at various dilution rates was performed using a modified Contois equation. The equation proposed here represents the conventional Contois equation as a particular equation of the modified formula ( m =1.0). The stability of the continuous fermentation in the production of Worcestershire sauce was evaluated, and this process was kinetically analyzed using the modified Contois equation. Neither decrease in yeast activity nor clogging with growth yeasts was observed in the trickle bed bioreactor with comb-shaped ceramic carriers during the fermentation period (about 6 months). From the results of the evaluation of mixing conditions this bioreactor can be regarded as a combination of a plug flow reactor (PFR) in the ceramic part, and a CSTR in the retention part. However, the trickle bed bioreactor could function as a CSTR having the same capacity as the actual volume of the retention part for the fermentation contribution rate of each part of the bioreactor. The observed ethanol concentration and productivity at the steady states were almost the same as the values calculated using the material balance equations of the sugar concentration and the ethanol concentration in a CSTR and the modified Contois equation with m =6.0. Thus, the modified Contois equation ( m =6.0) has been proposed as a design equation for a fermentation process for Worcestershire sauce production. When the modified Contois equation was applied to an acetic acid fermentation process and a plant tissue culture the observed product concentrations at each dilution rate were similar to the calculated values. It has been proved that the modified Contois equation is applicable not only to an alcohol fermentation process for Worcestershire sauce production but also to other fermentation processes and growth reactions.

NADPH-dependent d -xylose reductases (XRs) from Candida tropicalis IFO 0618 were purified and characterized. Mono Q HPLC revealed three XR isomers. The K m values of XR1, XR2 and XR3 for d -xylose were 37, 30 and 34 mM, and for NADPH 14, 18 and 9 μM, respectively. NADH did not act as a cofactor. The specificities of the three XRs for several aldoses were essentially the same. Gel filtration and cross-linking analysis showed that both XR1 and XR2 were dimers composed of identical subunits. The pI values of XR1 and XR2 were estimated to be 4.15 and 4.10, respectively. Comparison of the peptide maps of XR1 and XR2 showed that the molecular weights of 8 fragments of lysylendopeptidase-digested XR1 and XR2 were essentially the same as each other. The amino acid composition of each XR was also very similar. The molecular weights of XR1 and XR2 by mass spectra analysis were 36,497.91 and 36,539.68, respectively. The amino acid sequences of two XR1 peptide fragments (Nos. 4 and 5) were highly homologous with those of Pichia stipitis XR and mammalian aldose reductases.

A xylanase, which produces exclusively xylobiose from oat spelt and birch xylans, was isolated from the culture medium of Aeromonas caviae ME-1. The enzyme (xylanase V) was purified by ammonium sulfate fractionation, hydrophobic interaction, and ion-exchange and gel filtration chromatographies. The homogeneity of the final preparation was demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and agarose gel electrofocusing. The molecular mass and isoelectric point of the xylanase were 46 kDa and 5.4, respectively. Xylanase V had a maximum activity at a pH of 6.8 and at a temperature between 30 and 37°C. It was relatively stable at a pH between 5.0 and 8.6 and a temperature between 25 and 37°C. When soluble birch xylan was used as the substrate, the enzyme had a K m and V max of 2 mg/ml and 182 μmol of xylose equivalent liberated · min -1 · mg of protein -1 , respectively. By the action of xylanase V on xylans (from oat spelt and birch), only one product corresponding to xylobiose was observed by thin-layer chromatography. The xylanase V putative product was confirmed to be xylobiose by acid and enzymatic hydrolyses. The xylanase had neither β-xylosidase, α- l -arabinofuranosidase, cellulase, nor β-1,3-xylanase activities. Xylotriose was the shortest substrate which the enzyme could attack. These findings suggest that xylanase V is a novel enzyme that cleaves a xylobiose unit from one of the ends of xylans, probably by an exomechanism.

D-Xylose isomerase was purified to homogeneity from cell-free extracts of Bifidobacterium adolescentis by ammonium sulfate fractionation and chromatographies on DEAE-cellulose and Butyl-Toyopearl. The molecular weight of the purified enzyme was estimated to be 168,000 by gel filtration on TSKgel G-3000SW, and 53,000 on SDS-polyacrylamide gel electrophoresis. The optimum pH was around 7 and the enzyme was stable at pH 7-8. The enzyme required bivalent cations, Mg2+, Co2+, or Mn2+ for the activity, particularly Mn2+ to be best. The enzyme had a pI of 4.3, and the Km for D-xylose was 4 mM. The N-terminal amino acid sequence of the enzyme was not similar to those of D-xylose isomerases from other sources such as Clostridium thermosulfurogenes, Escherichia coli, or Bacillus subtilis.

ピーナッツ殻を24%KOHによるアルカリ処理と95%エタノールによる沈殿によってヘミセルロース画分を抽出した。この多糖類を10%硫酸にて100℃, 2時間加水分解すると薄層クロマトグラフィー上に単一のスポットが収率45.4%で得られ, それはD-キシロースと同定できた。また, この多糖類をAeromonas caviae ME-1とEnterobacter agglomerans ME-2の生産するキシラナーゼによって各々消化すると, 前者ではキシロースとキシロビオースが, 後者ではキシロースとキシロペンタオースがそれぞれ最終産物として得られた。

Sorbic acid (SOA), dehydroacetic acid (DA), benzoic acid (BA), and five esters of phydroxybenzoic acid (PHBA) in imported fruit vinegars were first passed through a Sep-Pak C18 cartridge and then analyzed simultaneously by gas-liquid chromatography. In brief, the vinegar samples were further acidified with hydrochloric acid, the test solution was saturated with sodium chloride and stirred vigorously, and the solution was put on the cartridge. Acetone as the solvent gave satisfactory results. A wide-bore capillary column was used for the gas chromatography. An FFAP column was most suitable for analysis of SOA, DA, and BA, and an MS column was most suitable for analysis of the five esters of PHBA in terms of stability, separability and sensitivity. Five fruit vinegars, fortified with 20μg/ml of eight food presertives, gave recovery of 91.6-100.5%, and the coefficient variation was 0.16% to 2.23%. The detection limit was 2μg/ml for each vinegar. This method could be used for various vinegars and was superior to conventional systematic methods for the assay of food preservatives. By this method, analytical results for 20 samples of imported fruit vinegars showed that SOA was present at the concertration of l.0-6.5μg/ml in two red wine vinegars, two sherry vinegars, and a balsamic vinegar. BA was detected at the concentration of 2.8μg/ml in a cider vinegar.

Worcestershire sauce production might include a fermentation step. The raw materials have high osmotic pressure, so we set out to select an osmotolerant yeast strain suitable for Worcestershire sauce production. Three commonly used yeasts were evaluated : Soccharomyces cerevisiae OC-2, a wine yeast;Kluyveromyces fragilis IFO 0288, widely used for fermentation of kefir grains ; and Zygosaccharomyces rouxii IFO 0493, a soy sauce yeast. In the range of total sugar Concentrations of 28.1-47.8% (the mixture contained sucrose, glucose, and fructose) cell numbers and ethanol production decreased as the sugar concentration rose, especially with K.fragilis. The relationship between the total sugar concentration and ethanol production by each yeast was expressed as follows : S.cerevisiae OC-2 (n=8, r=0.999) P=-1.54×10-4×S3+1.72×10-2×S2-0.649×S+8.91 K.fragilis IFO 0288 (n=8, r=0.995) P=(-3.57×10-2×S)+1.74 Z.rouxii IFO 0493 (n=8, r=0.987) P=-1.15×10-3×S2+9.38×10-2×S-1.36 Where P is the ethanol production and S is the total sugar concentration. Under the usual conditions for Worcestershire sauce production, with 39% total sugars, S.cerevisiae OC-2 had the greatest osmotolerance of the three yeasts, with higher ethanol productivity and satisfactory production of aromatic components than the other yeasts. We selected S.cerevisiae OC-2 for trial in the proposed new step in Worcestersbire sauce production.

ウスターソースに用いられる素材の野菜・果実 (トマト搾汁液, 野菜搾汁混合液) の発酵液の貯蔵性, およびその発酵液を利用した新しいウスターソースの製造法 (発酵法) を検討し以下の知見を得た。(1) トマト搾汁液のアルコール発酵条件は, 22.5±2.5℃で3日間と設定し, その発酵液は官能的に優れていた。(2) 野菜搾汁混合液の乳酸発酵条件は, 32.5±2.5℃で3日間と設定した。(3) アルコール発酵したトマト搾汁液は, 発酵後に食塩を3% (W/W) 添加すれば, 室温 (20～25℃) で15日間の貯蔵が可能であることがわかった。(4) 乳酸発酵した野菜搾汁混合液 [食塩4% (W/W)] は, 発酵後に食塩を5% (W/W) 添加すれば, 室温 (20～25℃) で15日間の貯蔵が可能であることがわかった。(5) 発酵工程を組み入れて製造したウスターソースは官能的に香味が優れ, ウスターソースへの発酵プロセス導入の有効性が示された。

The effect of culture conditions on xylitol production rate was investigated using Candida tropicalis IFO 0618. From the variance analysis of xylitol production rate, it was found that initial yeast extract concentration was highly significant (99%), while the interaction between D-xylose concentration and aeration rate was significant (95%). These results show the importance of initial yeast extract concentration and of the balance between D-xylose concentration and aeration in the production of xylitol. It was also clearly shown that C. tropicalis needed more yeast extract concentration for efficient xylitol production than for its growth. In order to enhance xylitol production rate, culture conditions were optimized by the Box-Wilson method. In this respect, initial D-xylose concentration, yeast extract concentration, and K(L)a were chosen as the independent factors in 2(3)-factorial experimental design. As the result of experiments, a maximum xylitol production rate of 2.67 g/L . h was obtained when initial D-xylose concentration and yeast extract concentration were 172.0 and 21.0 g/L, respectively, and K(L)a was 451.50 h(-1) by 90% oxygen gas.

Using bioreactors with yeasts, Zygosaccharomyces rouxii that undergoes ethanol fermentation and produces 2-phenyl ethanol, and Candida versatilis that produces 4-ethyl guaiacol, adsorbed-immobilized on a ceramic carrier, the total time required for production of soy sauce was shortened to 8 days without affecting the product’s quality.

In order to increase the rate of kojic production using Aspergillus oryzae , the initial glucose and Polypepton concentrations were optimized by the Box-Wilson method. A kojic acid production rate of 4.44 g/ l ·d was obtained when the initial glucose and Polypepton concentrations were 148.0 g/ l and 4.8 g/ l , respectively, at a K L a value of 164.7 h −1 .

A two-step fermentation process using Saccharomyces cerevisiae OC-2 (wine yeast) was studied. The first step, to multiply and immobilize yeast cells, was carried out by batch method (7 days) in a trickle bed bioreac-tor. In a second step, the substrate was continuously fermented by immobilized and free yeast cells in the same bioreactor. Continuous fermentation resulted in retention of 3% (W/V) of ethanol, 50 mg/L of isoamyl alcohol and 6 mg/L of β-phenethyl alcohol (the major aromatic components of fermented Worcestershire sauce). Maximum ethanol productivity was retained at 4.1–4.2 g/L/hr under continuous operation with immobilized yeasts, 3.2-fold higher than with the batch system.

A novel xylanase (xylanase IV) which produces xylotetraose as the only low-molecular-weight oligosaccharide from oat spelt xylan was isolated from the culture medium of Aeromonas caviae ME-1. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the xylanase IV molecular weight was 41,000. Xylanase IV catalyzed the hydrolysis of oat spelt xylan, producing exclusively xylotetraose. The acid hydrolysate of the product gave d-xylose. The enzyme did not hydrolyze either p-nitrophenyl-(beta)-d-xyloside, small oligosaccharides (xylobiose and xylotetraose), or polysaccharides, such as starch, cellulose, carboxymethyl cellulose, laminarin, and (beta)-1,3-xylan.

Two d -xylose reductase (XR) genes, xyrA and xyrB , of Candida tropicalis IFO 0618 were cloned and sequenced. Each XR gene had an open reading frame consisting of 324 amino acids (972 bp). The deduced amino acid sequences of each XR gene were very similar to each other, except for three amino acids. The molecular weights of the deduced gene products were 36,551 ( xyrA ) and 36,596 ( xyrB ). These genes were 73.0% identical to the Pichia stipitis XR gene.

The purpose of this study is to prepare Worcestershire sauce with higher levels of ethanol and aromatic components by a trickle bed bioreactor. Ethanol productivity in a trickle bed bioreactor was measured with changing circulation rates from 40 to 280 ml/min with a fixed aeration rate (200 ml/min) at 28°C. Compared with the lower circulation rate (40 ml/min), at 210 ml/min of circulation rate or higher, ethanol productivity increased 10.3-fold at 41 h of fermentation.

A 5.1 kb plasmid, pCDR1, which conferred cadmium resistance on Escherichia coli C600, was obtained during the cloning of the cadmium resistance gene from pGU100 harbored by cadmium-resistant Pseudomonas putida GAM-1, pCDR1 was constructed with pBR322 as vector and an about 800 bp inserted fragment. The nucleotide sequence revealed that the inserted DNA fragment was IS1. The cadmium resistance of this transformant was maintained even though the plasmid was cured. Southern analysis showed that the mobility of one band was changed, indicating that a chromosomal rearrangement occurred in the cadmium-resistant strain.

To investigate the role of hydrogen peroxide in Cr(VI) toxicity in vivo toward bacterial cells, we examined the effect of Cr(VI), hydrogen peroxide, sodium azide, and mannitol on the viability of Escherichia coli. Bacterial cells were incubated for 1 h with shaking in the presence of Cr(VI), hydrogen peroxide, sodium azide as catalase inhibitor, and/or mannitol as radical scavenger. The colony-forming ability and double-strand DNA degradation were examined. The viability assays revealed that Cr(VI) toxicity depended on hydroxyl radicals generated in the reaction involving hydrogen peroxide and chromium. Moreover, incubation of E. coli cells with 10 mM Cr(VI) and 3 mM hydrogen peroxide caused the degradation of double-strand DNA in vivo, which was suppressed by the addition of mannitol. These results indicated that hydroxyl radicals generated in the incubation degraded DNA of E. coli cells, resulting in cell death. In the absence of added hydrogen peroxide, the intracellular concentration of hydrogen peroxide in E. coli was low (below 1 microM). A catalase-defective strain incubated in the absence of added hydrogen peroxide remained fully viable after 1 h but showed decreased viability after prolonged incubation (4-8 h). The addition of mannitol suppressed this decrease, suggesting that hydroxyl radicals may be involved in the expression of Cr(VI) toxicity even without added hydrogen peroxide.

A strain of Byssochlamys sp. produced β-hydroxypropionic acid when grown on media containing high concentrations of acrylic acid. The maximal production of β-hydroxypropionic acid was 4.8% when the initial culture medium contained 7% acrylic acid and 2% glucose, and the initial culture pH was adjusted to 7.0. β-Hydroxypropionic acid production from acrylic acid depended greatly on the pH of the culture medium. Calcium hydroxide was the best neutralizer.

An NAD(P)H-dependent Cr(VI) reductase (molecular weight = 65,000) was purified from a Cr(VI)-resistant bacterium, Pseudomonas ambigua G-1. Stoichiometric analysis of the enzymatic reaction showed that the enzyme catalyzed the reduction of 1 mol of Cr(VI) to Cr(III) while consuming 3 mol of NADH as an electron donor. Chromium(VI) was reduced to Cr(V) by one equivalent NADH molecule in the absence of the enzyme. Electron spin resonance analysis showed that Cr(V) species (g = 1.979) was formed during the enzymatic reduction. The amount of Cr(V) species formed was about 10 times larger than that of the nonezymatic reduction. These findings show that the Cr(VI) reductase reduced Cr(VI) to Cr(III) with at least two reaction steps via Cr(V) as an intermediate.

When hexavalent chromium (Cr6+) tolerant Pseudomonas ambigua G-l was cultivated in nutrient broth containing 150 ppm Cr6 +, the Cr6+ content of the broth rapidly decreased. The Cr6+ reducing enzyme found in a cell-free extract of P. ambigua G-l required NADH but not NADPH as a hydrogen donor for the reduction of Cr6 +. The specific activities of cell-free extracts of several Cr6+ sensitive mutants derived from P. ambigua G-l showed decreases to one fourth to one tenth of that of P. ambigua G-l. Glucose protected the Cr6+ reducing enzyme against inac-tivation on dialysis.

A cadmium-sensitive mutant strain was isolated from a Cd2+-tolerant bacterium, Pseudomonas aeruginosa G-1 strain by mutagenesis with N-methyl-N′-nitro-N-mtrosoguanidine. The Cd2+-sensitive mutant strain was about 8-times as sensitive to Cd2+ and 2-times as sensitive to Hg2+, Cr2+ and achromycin, and not sensitive to Cu2+, as the parent strain.Vacuole-like substances were observed in the parent strain by transmission electron microscope in the presence of Cd2+, but not in the absence of Cd2+. The mutant strain took up 3.3-times the amount of Cd2+ into cells when compared with the parent strain. Disc electrophoretic patterns showed a characteristic protein band in the parent strain at the stationary phase, but the corresponding protein band was present in the mutant strain at the late exponential phase.

Three forms (I, II, and III) of R 5-P ketol icomerase (EC 5.3,1.6) were separated and purified from Candida utilis. The Kms for R 5-P by I, II, and III were 0.77 mM, 0.67 mM and 0.16 mM, respectively. The isoelectric points of the forms, I, II, and III were 3.79, 3.87 and 3.99, respectively.The activation energies of the forms, I, II, and III were 10,800, 12,000 and 6360 cal/mole, respectively. The forms, I, II, and III were all inhibited with chelating reagent, EDTA (1 mM), but not affected with thiol reagents such as p-CMB, ICH2COOH, NEM, and DTNB. These properties are quite different from the other known R 5-P ketol isomerases, all of those are not affected with EDTA, but inhibited with the thiol reagents as described above.

A base-specific ribonuclease (RNase) Lu (EC 3.1.27.5) was isolated and purified from Aspergillus niger in a yield of 23% by means of acetone precipitation, column chromatography on Duolite A-2, DEAE-cellulose, and 2'(3')-aminohexyl-5'-ATP-Sepharose 4B. The enzyme was shown to be homogeneous by disc-polyacrylamide gel electrophoresis. The molecular weight of the enzyme was estimated to be 43000 by both gel filtration and SDS-gel electrophoresis. The isoelectric point of the enzyme was determined to be 3.75 by isoelectric focusing. The enzyme had a base specificity: it released only 3'-UMP from yeast RNA or poly(U) and, in addition, small amounts of 3'-CMP from poly(C).

Pyruvate kinase (ATP: pyruvate 2-O-phosphotransferase, EC 2.7.1.40) from several yeasts were absorbed to blue dextran-Sepharose 4B and eluted with 1 M KCl in high yields. While pyruvate kinase of Candida guilliermodii AHU 4101 was eluted to some extent with phosphoenopyruvate (PEP), ADP or fructose, 1,6-diphosphate (FDP) individually from blue dextran-Sepharose 4B, the combination of FDP with PEP or ADP caused the complete elution of the kinase. Cibacron Blue competitively inhibited the pyruvate kinase with respect to both PEP and ADP at a saturated level of fixed substrate in the presence FDP, an allosteric activator. Further inhibition studies with Cibacron Blue suggest that one molecule of the blue dye binds per active site of the kinase at a saturate level of PEP, but two molecules of the dye bind per active site an unsaturated level of PEP in the presence of FDP.

The chemical components of ribonuclease L (RNase L) from Aspergillus sp. were tested in order to clarify the structure of the enzyme. The molecular weight and the number of the total anuno acid residues of the enzyme were about 4.5 × 104 and 393, respectively. The amino- and carboxyl-terminal amino acids of the enzyme were determined to be glycine and threonine, respectively. RNase L contained about 6% of neutral sugars and an glycopeptide was obtained by digestion with pronase. The isoelectric point of the enzyme was 3.47.

Phosphoglycerate mutases (EC 2.7.5.3) of several lactic acid bacteria were adsorbed to blue dextran-Sepharose 4B and eluted quantitatively with 1 M KC1. Phosphoglycerate mutase of Leuconostoc dextranicum AHU 1078 was eluted with 3-phosphoglycerate, 2-phosphoglycerate or 2,3-bisphosphoglycerate at 1 mM. Furthermore, ATP, ADP, GTP and GDP were also effective for eluting the mutase from the blue dextran-Sepharose column, but AMP and GMP were not. Although NADP(H) eluted the mutase, NAD(H) did not. By single step purification using linear gradient elution of 2,3-bisphosphoglycerate between 0 and 0.5 mM, the Leuconostoc mutase was purified to electrophoretic homogeneity with a 62.5% yield. The difference in spectrum of Cibacron Blue in the presence of the mutase was quite similar to that of the dye in the presence of KC1, but not in the presence of glycerol. The Leuconostoc mutase was inactivated by pyridoxal phosphate. This inactivation was prevented in the presence of blue dextran, as well as 3-phosphoglycerate.

p-Aminoazobenzene (PAAB) was degradated byBacillus subtilis. Both aniline and p-phenylenediamine as degradative compounds from PAAB were identified by thin layer chromatographic-, and high performance liquid chromatographic-methods. This fact suggests that the first degradative reaction of PAAB byB. subtilis is reductive fission of azo bond in PAAB.

In Osaka city, solid waste have been disposed in a pond at a sea‐based solid waste disposal site. The leachate is treated by the combined process of a facultative pond and an aerated lagoon. We examined the microflara of the combined process and clarified the relationship between leachate loading and microbial activities. BODs in the aerated lagoon was stably below 20 mgl−1 year round. The dominant genera in the aerated lagoon were Alcaligenes, Microcaccus, Maraxella, Aeramonas and Acinetabacter during the lower leachate loading period. There were no pathogenic bacteria of the genera Salmonella, Shigella and Vibrio in the aerated lagoon.

Candida utilis Ribose 5-phosphate ketol isomerase (EC 5.3.1.6) was purified. The enzyme is homogeneous by ultracentrifugal analysis and disc electrophoresis. The isoelectric point of the enzyme is 3.8, Km for R 5-P is 0.108 mM and Kis by 5′-AMP and 6-P-G are 0.16 mM and 0.61 mM, respectively. The thermodynamic parameters, ΔH, ΔG (35°C), ΔS (35°C) and E are 4336 cal/mole, — 5629 cal/mole, 32.15 cal/deg-mole and 6360 cal/mole, respectively. The molecular weight of the enzyme is 183,000 and the enzyme is assumed to consist of three subunits, one with a molecular weight of 75,000 and two identical subunits each with a molecular weight of 54,000.

An Hg2+-sensitive mutant strain was isolated from an Hg2+-tolerant bacterium Pseudomonas oleovorans G-1 strain by mutagenesis with N-methyl-N′-nitro-N-nitrosoguanidine. The Hg2+-sensitive mutant strain was about 10-times as sensitive to Hg2+ as the parent strain. Moreover, the mutant strain was considerably more sensitive to Cr6+ than the parent strain, but it did not show an appreciable change in sensitivity to Cd2+ and Cu2+. The mutant strain was considerably more sensitive to antibiotics achromycin, chloramphenicol and streptomycin than the parent strain. A more rigid structure was observed in the cell envelope of the mutant strain than the parent strain under transmission electron microscope. Higher amounts of DNA but less protein and RNA were found in the mutant strain compared to the parent strain. Disc electrophoretic patterns showed some differences in protein bands between the parent and mutant strain.