Sodium-Dependent Glutamate Uptake by an Alkaliphilic, Thermophilic Bacillus Strain, TA2.A1

A strain of Bacillus designated TA2.A1, isolated from a thermal spring in Te Aroha, New Zealand, grew optimally at pH 9.2 and 70 degrees C. Bacillus strain TA2.A1 utilized glutamate as a sole carbon and energy source for growth, and sodium chloride (>5 mM) was an obligate requirement for growth. Growth on glutamate was inhibited by monensin and amiloride, both inhibitors that collapse the sodium gradient (DeltapNa) across the cell membrane. N, N-Dicyclohexylcarbodiimide inhibited the growth of Bacillus strain TA2.A1, suggesting that an F1F0-ATPase (H type) was being used to generate cellular ATP needed for anabolic reactions. Vanadate, an inhibitor of V-type ATPases, did not affect the growth of Bacillus strain TA2.A1. Glutamate transport by Bacillus strain TA2.A1 could be driven by an artificial membrane potential (DeltaPsi), but only when sodium was present. In the absence of sodium, the rate of DeltaPsi-driven glutamate uptake was fourfold lower. No glutamate transport was observed in the presence of DeltapNa alone (i.e., no DeltaPsi). Glutamate uptake was specifically inhibited by monensin, and the Km for sodium was 5.6 mM. The Hill plot had a slope of approximately 1, suggesting that sodium binding was noncooperative and that the glutamate transporter had a single binding site for sodium. Glutamate transport was not affected by the protonophore carbonyl cyanide m-chlorophenylhydrazone, suggesting that the transmembrane pH gradient was not required for glutamate transport. The rate of glutamate transport increased with increasing glutamate concentration; the Km for glutamate was 2.90 microM, and the Vmax was 0.7 nmol. min-1 mg of protein. Glutamate transport was specifically inhibited by glutamate analogues.     

Biosorption of tungstate by a Bacillus sp. isolated from Anzali lagoon

An attempt was made to isolate bacterial strains capable of biologically removing tungstate (WO₄²⁻). Thirty-eight water samples were collected from various areas of Anzali lagoon, Iran. Initial screening of a total of 100 bacterial isolates at pH 5, resulted in the selection of one isolate with maximum adsorption capacity of 65.4 mg tungstate/g dry weight. It was tentatively identified as Bacillus sp. according to morphological and biochemical properties and named strain MGG-83. Tungsten concentration was measured spectrophotometrically using the dithiol method. Higher adsorption capacity was observed in the acidic pH ranging from 1 to 3. At pH 2, the strain removed 274.4 mg tungstate/g dry weight within 5 min from the solution with 300 mg WO₄²⁻/l initial concentration and thereafter adsorption rate decreased remarkably. The applicability of the Freundlich isotherm for representation of the experimental data was investigated. Using 1 mM sodium azide and 10 mM 2,4−dinitrophenol, it was shown that only 20% reduction occurred in adsorption and steam sterilization of the bacterial cells resulted in 11% decrease in tungstate uptake. Temperature variations (20–40°C) had no significant effect on tungstate uptake. Pretreatment with the cations had no effect in uptake but pretreatment with anions decreased the tungstate uptake as indicated: sulfate > chromate > nitrate > molybdate > selenate > rhenate. Tungstate was removed from metal-laden biomass after desorption treatments by addition of different desorbing solutions with the results sodium acetate > EDTA > NaCl > KOH > H₂SO₄.     

Nickel tolerance and accumulation by bacteria from rhizosphere of nickel hyperaccumulators in serpentine soil ecosystem of Andaman, India

Rhizosphere microorganisms harboring nickel hyperaccumulators, Rinorea bengalensis (Wall.) O. K. and Dichapetalum gelonioides ssp. andamanicum (King) Leenh. endemic to serpentine outcrops of Andaman Islands, India, were screened for their tolerance and accumulation of Ni. The rhizosphere soils from both the plants were rich in total and available Ni along with Co, Cr, Fe and Mg but poor in microbial density and were dominated by bacteria. Out of total 123 rhizosphere microorganisms (99 bacteria and 24 fungi), bacteria were more tolerant to Ni than fungi. Viable cells of selected Ni-tolerant bacterial isolates (MIC = 13.6–28.9 mM Ni) belonging to Pseudomonas, Bacillus and Cupriavidus were capable of accumulating nickel (209.5–224.0 μM Ni g⁻¹ protein) from aqueous solution. Cupriavidus pauculus KPS 201 (MTCC 6280), showing highest degree of nickel tolerance (MIC 28.9 mM Ni) and uptake (224.0 μM Ni g⁻¹ protein, 60 min) was used for detailed study. Kinetics of nickel uptake in C. pauculus KPS 201 followed a linearized Lineweaver-Burk plot. The K _m and V _max for nickel uptake by minimal medium grown-cells approximated 1.5 mM Ni and 636.9 μM Ni g⁻¹ protein, respectively. The uptake process was inhibited by Co, Cu, Cd, Mg, Mn and Zn, however, complete inhibition was not achieved even in presence of 500 mM Mg. Metabolic inhibitors, sodium azide (1.0 mM) and carbonyl cyanide m-chlorophenylhydrazone (0.4 mM) strongly inhibited nickel uptake suggesting the process as an energy dependent one. The present study clearly shows that bacteria in the rhizosphere of Ni-hyperaccumulators are capable of tolerating high concentration of Ni and also possesses nickel uptake potential. The Ni-hyperaccumulators in combination with these Ni-resistant bacteria could be an ideal tool for nickel bioremediation.     

65Zn2+ transport by isolated gill epithelial cells of the American lobster, Homarus americanus

Gills are the first site of impact by metal ions in contaminated waters. Work on whole gill cells and metal uptake has not been reported before in crustaceans. In this study, gill filaments of the American lobster, Homarus americanus, were dissociated in physiological saline and separated into several cell types on a 30, 40, 50, and 80% sucrose gradient. Cells from each sucrose solution were separately resuspended in physiological saline and incubated in ⁶⁵Zn²⁺ in order to assess the nature of metal uptake by each cell type. Characteristics of zinc accumulation by each kind of cell were investigated in the presence and absence of 10 mM calcium, variable NaCl concentrations and pH values, and 100 μM verapamil, nifedipine, and the calcium ionophore A23187. ⁶⁵Zn²⁺ influxes were hyperbolic functions of zinc concentration (1–1,000 μM) and followed Michaelis–Menten kinetics. Calcium reduced both apparent zinc binding affinity (K _m) and maximal transport velocity (J _max) for 30% sucrose cells, but doubled the apparent maximal transport velocity for 80% sucrose cells. Results suggest that calcium, sodium, and protons enter gill epithelial cells by an endogenous broad-specificity cation channel and trans-stimulate metal uptake by a plasma membrane carrier system. Differences in zinc transport observed between gill epithelial cell types appear related to apparent affinity differences of the transporters in each kind of cell. Low affinity cells from 30% sucrose were inhibited by calcium, while high affinity cells from 80% sucrose were stimulated. ⁶⁵Zn²⁺ transport was also studied by isolated, intact, gill filament tips. These intact gill fragments generally displayed the same transport properties as did cells from 80% sucrose and provided support for metal uptake processes being an apical phenomenon. A working model for zinc transport by lobster gill cells is presented.     

The obligate alkaliphile <Emphasis Type="Italic">Bacillus clarkii</Emphasis> K24-1U retains extruded protons at the beginning of respiration

Alkaliphiles grow under alkaline conditions that might be disadvantageous for the transmembrane pH gradient (ΔpH, outside acidic). In this study, the behaviors of extruded protons by the respiration of obligate alkaliphilic Bacillus clarkii K24-1U were investigated by comparison with those of neutralophilic Bacillus subtilis IAM 1026. Although whole-cell suspensions of both Bacillus species consumed oxygen immediately after the addition of air, there were lag times before the suspensions were acidified. Under alkaline conditions, the lag time for B. clarkii significantly increased, whereas that for B. subtilis decreased. In the presence of valinomycin or ETH-157, which disrupts the membrane electrical potential (Δψ), the cell suspensions of both Bacillus species acidified immediately after the addition of air. Artificial electroneutral antiporters (nigericin and monensin) that eliminate the ΔpH exhibited no significant effect on the lag times of the two Bacillus species except that monensin increased the lag times of B. clarkii. The inhibition of ATPase and the Na⁺ channel also exhibited little effects on the lag times. The increased lag time for B. clarkii may represent the Δψ-dependent proton retention on the outer surface of the cytoplasmic membrane to generate a sufficient ΔpH under alkaline conditions.     

Molecular and enzymatic characterization of a subfamily I.4 lipase from an edible oil-degrader <Emphasis Type="Italic">Bacillus</Emphasis> sp. HH-01

An edible-oil degrading bacterial strain HH-01 was isolated from oil plant gummy matter and was classified as a member of the genus Bacillus on the basis of the nucleotide sequence of the 16S rRNA gene. A putative lipase gene and its flanking regions were cloned from the strain based on its similarity to lipase genes from other Bacillus spp. The deduced product was composed of 214 amino acids and the putative mature protein, consisting of 182 amino acids, exhibited 82% amino acid sequence identity with the subfamily I.4 lipase LipA of Bacillus subtilis 168. The recombinant product was successfully overproduced as a soluble form in Escherichia coli and showed lipase activity. The gene was, therefore, designated as lipA of HH-01. HH-01 LipA was stable at pH 4–11 and up to 30°C, and its optimum pH and temperature were 8–9 and 30°C, respectively. The enzyme showed preferential hydrolysis of the 1(3)-position ester bond in trilinolein. The activity was, interestingly, enhanced by supplementing with 1 mM CoCl₂, in contrast to other Bacillus lipases. The lipA gene seemed to be constitutively transcribed during the exponential growth phase, regardless of the presence of edible oil.     

Regulation of leucine transport by intracellular pH in Bacillus pasteurii

The kinetics, specificity and mechanism of leucine uptake were studied in the alkaliphilic bacterium Bacillus pasteurii DSM 33 (ATCC 11859). Leucine was accumulated up to 200-fold by a sodium-dependent secondary transport system for branched-chain amino acids. Apparent K_t values of 9.6 μM for leucine, 8.9 μM for isoleucine, 9.3 μM for valine, and 0.71 mM for sodium were determined, and maximum uptake activity was observed at an external pH of 8.5 and at 35°C. The effect of several ionophores indicated that transport was energized by the membrane potential and a sodium gradient; each gradient alone was sufficient to drive the uptake of leucine. The activity of the leucine transport system was regulated by the intracellular pH and was inhibited at an internal pH below 7.0. Received: 26 September 1995 / Accepted: 10 December 1995     

Characteristics of the sucrose uptake system of vacuoles isolated from red beet tissue. Kinetics and specifity of the sucrose uptake system

The uptake of sucrose against a concentration gradient into the dextran-impermeable [³H]H₂O space of red beet (Beta vulgaris L.) vacuoles has been studied using silicone-layer-filtering centrifugation on both fluorometric and ¹⁴C-measurement of sucrose. Sucrose transport into vacuoles proceeds partly by an active transport system and partly by passive permeation. The K _M(20°C) for active sucrose uptake was found to be about 22 mM and the V _Max(20°C) was about 174 nmol sucrose x (unit betacyanin)^-1 x h^-1. The temperature dependency of sucrose transport appears to have an activation energy of 35,0 KJ×mol^-1. Among various mono-, di-, and trisaccharides tested, raffinose acts as a competitive inhibitor of sucrose uptake.Abbreviations EDTA ethylenediamine tetraacetic acid - fr. wt. fresh weight - Tris tris-(hydroxymethyl)-aminomethan     

Cloning, purification, and characterization of chitosanase from Bacillus sp. DAU101

A chitosanase-producing Bacillus sp. DAU101 was isolated from Korean traditional food. This strain was identified on the basis of phylogenetic analysis of the 16S rDNA sequence, gyrA gene, and phenotypic analysis. The gene encoding chitosanase (csn) was cloned and sequenced. The csn gene consisted of an open reading frame of 837 nucleotides and encodes 279 amino acids with a deduced molecular weight of 31,420 Da. The deduced amino acid sequence of the chitosanase from Bacillus sp. DAU101 exhibits 88 and 30 % similarity to those from Bacillus subtilis and Pseudomonas sp., respectively. The chitosanase was purified by glutathione S-transferase fusion purification system. The molecular weight of purified enzyme was about 27 kDa, which suggests the deletion of a signal peptide by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. The pH and temperature optima of the enzyme were 7.5 and 50 °C, respectively. The enzyme activity was increased by about 1.6-fold by the addition of 5 or 10 mM Ca²⁺. However, Hg²⁺ and Ni⁺ ions strongly inhibited the enzyme. The enzyme produced, GlcN_2–4, were the major products from a soluble chitosan.     

Zinc biosorption by a zinc-resistant bacterium, Brevibacterium sp. strain HZM-1

A zinc-resistant bacterium, Brevibacterium sp. strain HZM-1 which shows a high Zn²⁺-adsorbing capacity, was isolated from the soil of an abandoned zinc mine. Kinetic analyses showed that Zn²⁺ binding to HZM-1 cells follows Langmuir isotherm kinetics with a maximum metal capacity of 0.64 mmol/g dry cells and an apparent metal dissociation constant of 0.34 mM. The observed metal-binding capacity was one of the highest values among those reported for known microbial Zn²⁺ biosorbents. The cells could also adsorb heavy metal ions such as Cu²⁺. HZM-1 cells could remove relatively low levels of the Zn²⁺ ion (0.1 mM), even in the presence of large excess amounts (total concentration, 10 mM) of alkali and alkali earth metal ions. Bound Zn²⁺ ions could be efficiently desorbed by treating the cells with 10 mM HCl or 10 mM EDTA, and the Zn²⁺-adsorbing capacity of the cells was fully restored by treatment of the desorbed cells with 0.1 M NaOH. Thus, HZM-1 cells can serve as an excellent biosorbent for removal of Zn²⁺ from natural environments. The cells could grow in the presence of significant concentrations of ZnCl₂ (at least up to 15 mM) and thus is potentially applicable to in situ bioremediation of Zn²⁺-contaminated aqueous systems. Received: 1 February 2000 / Received revision: 31 March 2000 / Accepted: 1 May 2000     

The Transport of Sugars in Developing Fruits of Satsuma Mandarin

Transport of sugars to the juice sacs of developing satsumamandarin (Citrus unshui Marc) has been studied in attached fruitsand in isolated fruit pieces. ¹⁴CO₂ fed to the leaves resultedin [¹⁴C]sugar accumulation in the juice sacs, mainly as [¹⁴C]sucrose.Uptake of sucrose and glucose by the excised fruit pieces proceededlinearly with time. Sucrose uptake was linearly related to sucroseconcentration over the range 25–300 mM, with no indicationof saturation. This uptake was insensitive to pH (5, 7 or 9),Ca²⁺(3 mM), PCMBS (2.5 mM), DNP (1 mM) or vanadate (0.1 mM)but was slightly reduced by erythrosin (21 % by 0–1 mM;27 % by 1 mM). No competitive effect of glucose (up to 100 mM)was detectable on sucrose uptake from 100 mM solution. Mostof the [¹⁴C]sucrose uptake observed was reversible, althoughconsiderable hydrolysis and metabolic conversion were evidenced.A vanadate-sensitive ATPase was demonstrated by EM localizationon the plasma membrane of the juice sac cells. These resultsare interpreted in relation to the accumulation of assimilatesby the developing fruit. Transport: sugar, satsuma mandarin, juice sacs     

Glutamine uptake by a sodium-dependent secondary transport system inCorynebacterium glutamicum

Corynebacterium glutamicum took up glutamine by a sodium-dependent secondary transport system. Both the membrane potential and the sodium gradient were driving forces. Glutamine uptake showed Michaelis-Menten kinetics, with aK _m of 36 μM and aV _max of 12.5 nmol min⁻¹ (mg dry weight)⁻¹ at pH 7. Despite a pH optimum in the alkaline range around pH 9, it was shown that uncharged glutamine is the transported species. The affinity for the cotransported sodium was relatively low; an apparentK _m of 1.4 mM was determined. Among various substrates tested, only asparagine, when added in 50-fold excess, led to an inhibition of glutamine transport. It was concluded that glutamine uptake occurs via a specific transport system in symport with at least one sodium ion.     

Purification and biochemical characterization of the F1Fo-ATP synthase from thermoalkaliphilic Bacillus sp. strain TA2.A1

We describe here purification and biochemical characterization of the F(1)F(o)-ATP synthase from the thermoalkaliphilic organism Bacillus sp. strain TA2.A1. The purified enzyme produced the typical subunit pattern of an F(1)F(o)-ATP synthase on a sodium dodecyl sulfate-polyacrylamide gel, with F(1) subunits alpha, beta, gamma, delta, and epsilon and F(o) subunits a, b, and c. The subunits were identified by N-terminal protein sequencing and mass spectroscopy. A notable feature of the ATP synthase from strain TA2.A1 was its specific blockage in ATP hydrolysis activity. ATPase activity was unmasked by using the detergent lauryldimethylamine oxide (LDAO), which activated ATP hydrolysis >15-fold. This activation was the same for either the F(1)F(o) holoenzyme or the isolated F(1) moiety, and therefore latent ATP hydrolysis activity is an intrinsic property of F(1). After reconstitution into proteoliposomes, the enzyme catalyzed ATP synthesis driven by an artificially induced transmembrane electrical potential (Deltapsi). A transmembrane proton gradient or sodium ion gradient in the absence of Deltapsi was not sufficient to drive ATP synthesis. ATP synthesis was eliminated by the electrogenic protonophore carbonyl cyanide m-chlorophenylhydrazone, while the electroneutral Na(+)/H(+) antiporter monensin had no effect. Neither ATP synthesis nor ATP hydrolysis was stimulated by Na(+) ions, suggesting that protons are the coupling ions of the ATP synthase from strain TA2.A1, as documented previously for mesophilic alkaliphilic Bacillus species. The ATP synthase was specifically modified at its c subunits by N,N'-dicyclohexylcarbodiimide, and this modification inhibited ATP synthesis.     

A novel thermoacidophilic endoglucanase, Ba-EGA, from a new cellulose-degrading bacterium, Bacillus sp.AC-1

A newly discovered bacterium, strain AC1, containing cellulase was isolated from the gastric juice of the mollusca, Ampullaria crosseans. Analysis of the 16S rDNA sequence and carbon sources revealed that the bacterium belonged to the genus Bacillus. A novel endoglucanase (Ba-EGA) was purified from culture supernatants of the bacterium growing in CMC-Na (low viscosity) induction medium. The cellulase was purified about 150-fold by ammonium sulfate fractionation, ion exchange, hydrophobic, and gel filtration chromatography, with a specific activity of 35.0 IU/mg. The molecular mass of the enzyme was 67 kDa. N-terminal amino acid sequencing revealed a sequence of SDYNYVEVLQKSILF, which had high homology with endoglucanases from the Bacillus and Clostridium species. The maximal activity of the enzyme with the substrate of CM-cellulose is at pH 4.5–6.5 and 70°C, respectively. The studies on pH and temperature stability showed that the Ba-EGA is stable enough between pH 7.5 and 10.5 at 30°C for 2 h, and more than 80% of the activity still remains when incubation was prolonged to 1 h at 50°C. The activity of the enzyme was significantly inhibited by Fe²⁺, Cu²⁺ (5.0 mM of each), and sodium dodecyl sulfate (SDS) (0.5%) and obviously activated by Tween 20 and Triton X-100 (0.25% each). Binding studies revealed that the Ba-EGA had cellulose-binding domain.     

Studies on non-symbiotic diazotrophic bacterial populations of coastal arable saline soils of India

The effect of fluctuations of salinity in three different seasons on diazotrophic populations and N₂ fixation in six mono cropped rice field soils of the coastal region of the Gangetic delta of West Bengal, India, was studied. The average pH, ECe, organic carbon and total nitrogen of the soils ranged from 4.99–7.08, 2.02–19.58 dSm⁻¹, 4.68–12.03 g kg⁻¹ and 0.44–1.70 g kg ⁻¹, respectively. The average log colony forming units of the bacterial populations and N₂-fixation in the soils varied from 4.61 to 5.86 and 2.74 to 4.52 mg N₂ fixed 50 ml ⁻¹ culture media respectively, with the lowest value recorded in summer. Recovery of microorganisms and N₂- fixation gradually decreased with extraneous addition of NaCl in the culture media. All the eight isolates were Gram positive, spore and capsule formers. They could utilize glucose, sucrose, mannitol, starch, citrate and nitrate, and were catalase and gelatinase positive, but indole, methyl red and Vogues Proskauer reaction negative. The organisms produced alkaline reaction on TSI agar slant. The acetylene reduction assay of the isolates at 0 and 1% NaCl in the culture media were 4.51–164.52 and 1.72–100.6 nmole C₂H₄ ml⁻¹ culture media in 72 h, respectively. The isolates could fix 2.42–4.45 and 2.04–4.08 mg N₂ fixed 50 ml⁻¹ culture media at 0 and 1% NaCl in the culture media respectively. 16S rDNA sequences of the isolates were similar to the species: Bacillus sp. isolate 28A, Bacillus sp. MOLA 87, Bacillus sp. By113 (B)Ydz-dh, Bacillus sp. PN13, Bacillus licheniformis strain RH101, Bacterium Antarctica 14, Bacillus sp. PN13 and Bacillus megaterium.     

Functional characterization of a LAHC sucrose transporter isolated from grape berries in yeast

Large amounts of sugar are imported into grape berries from source leaves during ripening, and sucrose transporters play a key role during this process. In this study, a putative grape sucrose transporter gene VvSUC27, primarily expressed in sink tissue, was transformed into a yeast strain to characterize its function as a sucrose transporter. Sucrose was taken up by yeast transformed with VvSUC27 at an optimum pH of 4.0–5.0 and a K _m of 8.0–10.5 mM, indicating VvSUC27 is a LAHC (low-affinity/high-capacity) sucrose transporter. The ability of sucrose uptake in transformed yeast was activated by monosaccharides and inhibited by maltose and DEPC. Ya Li Zhang and Qing Yong Meng contributed equally to the paper.     

Antibacterial activity of cyclodextrins against <Emphasis Type="Italic">Bacillus</Emphasis> strains

Growth of alkaliphilic Bacillus halodurans C-125 both on agar plates and in liquid culture was inhibited by methyl-β-cyclodextrin (CD). Furthermore, resting cells of the strain were lysed by contact with methyl-β-CD higher than 10 mM. α-CD also showed lysis activity against Bacillus and related strains. The activity was not observed with Gram-negative and Gram-positive bacteria except for Bacillus strains. Fluorescence staining and scanning electron microscopy of cells revealed that methyl-β-CD disrupted cell membranes, and consequently, the cells were lysed. This is a novel physiological property of CDs.     

Inhibition by nisin of K+ uptake in a sensitivePediococcus sp. strain

Summary A nisin-sensitive strain ofPediococcus sp possessed an uptake system for K⁺ which was apparently dependent on metabolic energy and ATPase activity. K⁺ uptake rate was dependent on the glucose and K⁺ concentrations and showed approximately Michaelis-Menten kinetics with respect to both of these variables with K_t values of 1.2 mM and 599 μM respectively. The presence of nisin inhibited K⁺ uptake with the percentage inhibition proportional to the nisin activity,. Total inhibition occurred at between 4.5 and 5.0 IU ml⁻¹ and the MIC was approximately 0.6 IU ml⁻¹.     

Isolation and partial characterization of an antibacterial substance produced by Enterococcus faecium

A strain ofEnterococcus faecium isolated from Bulgarian yellow cheese “kashkaval” produced a bacteriocin-like substance named enterococcin A 2000. The antibacterial substance had a low molar mass (<2 kDa), was relatively stable toward heat but was sensitive to selected proteolytic enzymes. It was active against Gram-positive bacteria including enterococci, such asListeria, Bacillus andStreptococcus, and also against Gram-negativeE. coli. Production of enterococcin A 2000 has a maximum near the end of the exponential phase of producer growth. The peptide was purified by ammonium sulfate precipitation, butanol extraction, followed by cation-exchange chromatography and reversed-phase chromatography. A partial sequence of purified enterococcin A 2000 indicated that this substance does not belong to the class IIa of bacteriocins presenting the consensus anti-Listeria motif YGNGV.     

Deficiency in frataxin homologue YFH1 in the yeast Pichia guilliermondii leads to missregulation of iron acquisition and riboflavin biosynthesis and affects sulfate assimilation

Pichia guilliermondii is a representative of yeast species that overproduce riboflavin (vitamin B₂) in response to iron deprivation. P. guilliermondii YFH1 gene coding for frataxin homologue, eukaryotic mitochondrial protein involved in iron trafficking and storage, was identified and deleted. Constructed P. guilliermondii Δyfh1 mutant grew very poorly in a sucrose-containing synthetic medium supplemented with sulfate or sulfite as a sole sulfur source. Addition of sodium sulfide, glutathione, cysteine, methionine, N-acetyl-l-cysteine partially restored growth rate of the mutant suggesting that it is impaired in sulfate assimilation. Cellular iron content in Δyfh1 mutant was ~3–3.5 times higher as compared to the parental strain. It produced 50–70 times more riboflavin in iron sufficient synthetic media relative to the parental wild-type strain. Biomass yield of the mutant in the synthetic glutathione containing medium supplemented with glycerol as a sole carbon source was 1.4- and 2.6-fold increased as compared to sucrose and succinate containing media, respectively. Oxygen uptake of the Δyfh1 mutant on sucrose, glycerol or succinate, when compared to the parental strain, was decreased 5.5-, 1.7- and 1.5-fold, respectively. Substitution of sucrose or glycerol in the synthetic iron sufficient medium with succinate completely abolished riboflavin overproduction by the mutants. Deletion of the YFH1 gene caused hypersensitivity to hydrogen peroxide and exogenously added riboflavin and led to alterations in superoxide dismutase activities. Thus, deletion of the gene coding for yeast frataxin homologue has pleiotropic effect on metabolism in P. guilliermondii.