Inheritance studies with inbred lines of maize having different activity levels of the AP 1 controlled acid phosphatase isozymes

Summary The genetic control of acid phosphatase-1 (AP ₁) activity in pollen of maize was studied by crossing inbred lines having different AP ₁ isozymes and different activity levels of the A P ₁ enzyme. Usually, the intensities of the SS and FF isozyme bands were not equal in pollen of A P ₁ ^S /A P ₁ ^F heterozygous F ₁ hybrids, but the relative intensities of the two bands were not correlated to the activity levels of the parental lines. The A P ₁ ^S /A P ₁ ^S and A P ₁ ^F /A P ₁ ^F F ₂ populations differed in their mean level of activity. Both populations showed segregation in the activity levels indicating single gene control. The intensity ratios of the SS and FF bands in the different heterozygous A P ₁ ^S /A P ₁ ^F F ₂ plants did not segregate. The results support the competition model for gene regulation proposed by Schwartz (1971).     

Comparative thermoregulatory adaptations of field mice of the genus Apodemus to habitat challenges

Thermoregulatory abilities, which may play a role in physiological adaptations, were compared between two field mouse species (Apodemus mystacinus and A. hermonensis) from Mount Hermon. While A. hermonensis is common at altitudes above 2100 m, A. mystacinus is common at 1650 m. The following variables were compared in mice acclimated to an ambient temperature of 24°C with a photoperiod of 12L:12D, body temperature during exposure to 4°C for 6 h, O₂ consumption and body temperature at various ambient temperature, non-shivering thermogenesis measured as a response to a noradrenaline injection, and the daily rhythm of body temperature. Both species could regulate their body temperature at ambient temperatures between 6 and 34°C. The thermoneutral zone for A. mystacinus lies between 28 and 32°C, while for A. hermonensis a thermoneutral point is noted at 28°C. Both species increased O₂ consumption and body temperature as a response to noradrenalin. However, maximal VO ₂ consumption as an response to noradrenaline and non-shivering thermogenesis capacity were higher in A. mystacinus, even though A. hermonensis is half the size of A. mystacinus. The body temperature rhythm in A. hermonensis has a clear daily pattern, while A. mystacinus can be considered arhythmic. The results suggest that A. hermonensis is adapted to its environment by an increase in resting metabolic rate but also depends on behavioural thermoregulation. A. mystacinus depends more on an increased non-shivering thermogenesis capacity.Abbreviations C thermal conductance - NA noradrenaline - NST non-shivering thermogenesis - OTC overall thermal conductance - RMR resting metabolic rate - STPD standard temperature and pressure dry - T _a ambient temperature - T _b body temperature - I _b Min minimal T _b , measured before NA iniection - T _b NA maximal - T _b as a response to NA injection - T _lc lower critical point - TNP thermoneutral point - TNZ thermoneutral zone - VO₂ O₂ consumption - VO₂ Min minimal VO₂ measured before NA injection - VO₂NA maximal VO₂, as a response to NA injection     

Enzymes and coenzymes of the carbon monoxide dehydrogenase pathway for autotrophic CO2 fixation in Archaeoglobus lithotrophicus and the lack of carbon monoxide dehydrogenase in the heterotrophic A. profundus

Archaeoglobus lithotrophicus is a hyperthermophilic Archaeon that grows on H₂ and sulfate as energy sources and CO₂ as sole carbon source. The autotrophic sulfate reducer was shown to contain all the enzyme activities and coenzymes of the reductive carbon monoxide dehydrogenase pathway for autotrophic CO₂ fixation as operative in methanogenic Archaea. With the exception of carbon monoxide dehydrogenase these enzymes and coenzymes were also found in A. profundus. This organism grows lithotrophically on H₂ and sulfate, but differs from A. lithotrophicus in that it cannot grow autotrophically: A. profundus requires acetate and CO₂ for biosynthesis. The absence of carbon monoxide dehydrogenase in A. profundus is substantiated by the observation that this organism, in contrast to A. lithotrophicus, is not mini-methanogenic and contains only relatively low concentrations of corrinoids.Abbreviations F ₄₂₀ coenzyme F₄₂₀ - MFR methanofuran - CHO-MFR formylmethanofuran - H ₄MPT 5,6,7,8-tetrahydromethanopterin - CHO–H ₄MPT N⁵ formyl-H₄MPT - CHH₄MPT⁺N⁵ methenyl-H₄MPT - CH ₂=H₄MPT N⁵, N¹⁰ methylene-H₄MPT - CH ₃–H₄MPT N⁵ methyl-H₄MPT - H ₄F tetrahydrofolate - I U 1 mol/min - t _d doubling time     

Evolution of the mandibular third premolar crown in early Australopithecus

The Pliocene hominins Australopithecus anamensis and Australopithecus afarensis likely represent ancestor-descendent taxa—possibly an anagenetic lineage—and capture significant change in the morphology of the canine and mandibular third premolar (P₃) crowns, dental elements that form the canine honing complex in nonhuman catarrhines. This study focuses on the P₃ crown, highlighting plesiomorphic features in A. anamensis. The A. afarensis P₃ crown, in contrast, is variable in its expression of apomorphic features that are characteristic of geologically younger hominins. Temporal variation characterizes each taxon as well. The A. anamensis P₃ from Allia Bay, Kenya expresses apomorphic character states, shared with A. afarensis, which are not seen in the older sample of A. anamensis P₃s from Kanapoi, Kenya, while spatiotemporal differences in shape exist within the A. afarensis hypodigm. The accumulation of derived features in A. afarensis results in an increased level of P₃ molarisation. P₃ molarisation did not evolve concurrent with postcanine megadontia and neither did the appearance of derived aspects of P₃ occlusal form coincide with the loss of canine honing in hominins, which is apparent prior to the origin of the genus Australopithecus. A. afarensis P₃ variation reveals the independence of shape, size, and occlusal form. The evolution of the P₃ crown in early Australopithecus bridges the wide morphological gap that exists between geologically younger hominins on the one hand and extant apes and Ardipithecus on the other.     

Development and ossification of the feeding apparatus in the larvae of two co‐occurring species of kob (Sciaenidae), Argyrosomus japonicus and Argyrosomus inodorus,in South Africa

The teeth of the oral jaws of two sympatric species of Argyrosomus, Argyrosomus japonicus and Argyrosomus inodorus, found along the South African coast developed first on the premaxilla and then on the dentary of the lower jaw. Teeth were observed on the premaxilla of A. inodorus [head length (L_H) = 1·0 mm; notochord length (L_N) = 2·7 mm] at a smaller size than in A. japonicus (L_H = 1·2 mm; L_N = 4·7 mm). The ventral elements of the gill arches (hypo‐ and basibranchials) were not ossified by the end of preflexion. The fifth ceratobranchial began ossifying and possessed pharyngeal teeth by 1·2 mm L_H (L_N = 4·7 mm) in A. japonicus and 1·1 mm L_H (L_N = 3·2 mm) in A. inodorus. To complement the osteological data, stomach contents were also analysed as a proxy for feeding apparatus functionality. Prey were first present in the stomach of A. japonicus at 1·2 mm L_H (L_N = 4·7 mm) and only 22% of the stomachs contained no prey suggesting that A. japonicus is already actively foraging by preflexion. In comparison, 83% of the stomachs of A. inodorus contained no prey and a single prey item was present in the largest examined specimen (L_H = 1·6 mm; L_N = 5·4 mm). Elements of the feeding apparatus begin to ossify early during ontogeny. While the overall pattern of ossification is similar between the two species, A. japonicus may be able to begin feeding at smaller head lengths relative to A. inodorus in their nursery habitats.     

Effect of the nitrogen source on the biosynthesis, composition, and structure of the exopolysaccharides ofAureobasidium pullulans (de Bary) Arnaud

The effect of the nitrogen source and the C/N ratio of the growth medium on the biosynthesis, composition, and structure of the exopolysaccharides (EPSs) ofAureobasidium pullulans (de Bary) Arnaud var.aubasidani Yurlova var. nov. andA. pullulans var.pullulans was studied.A. pullulans var.pullulans andA. pullulans var.aubasidani strains synthesized the maximum amounts of EPSs in the presence of, respectively, a reduced nitrogen source ((NH₄)₂SO₄) and an oxidized nitrogen source (NaNO₃) in the medium. The data presented confirm the validity of using the chemical composition and structure of the major cetavlon-precipitated fraction ofA. pullulans EPSs for the characterization of intraspecies taxa.     

Thermodynamics of oligo (A) N -2poly(U) from the dependence of the temperature of the helix-coil transition on oligomer concentration

On the basis of elementary two-state, ideal solution thermocynamics, a modified expression for the melting of oligo. polynucleotide helices is derived which is applicable to variations in T_m^N and/or oligomer concentration, C_m with oligomer length, N: ((I)) ΔH_r is the enthalpy per helix residue, i.e., per base-pair or base-triplet, V_r^f is the thermodynamic “available” or “reaction” volume, in liters/mole of helical residues; and n is the number of polynucleotide strands, e.g., n = 2 for oligo (A)_N·2 poly(U)∞. Some earlier treatments have engendered confusion in the interpretation of the “reaction volume,” but with the derivation herein, the entropic origin and physical significance of V_r^f is unequivocal. The following approximation was arrived at for the reduction expected in the configurational entropy, ΔS_r^{conf, ∞}, for (A)∞·2(U)∞, when the poly(A), strand is substituted for by an equivalent strand of contiguous oligo(A)_N,′s: ((II)) This adjustment of ΔS_r^{conf, ∞} represents the source of the coefficient to 1/T_m^∞ in expression (I). The expectation that ΔS_r^{conf, N} < ΔS_r^{conf, ∞} is due to the effect of releasing normal internucleotide configurational restrictions every Nth residue in one-third of the strands of the (A)_N·2(U)∞ helix. Although the reduction in ΔS_r^{conf, ∞} (II) may seem small (i.e., only 5.5% for the tetramer), its effect on the magnitude of V_r^f in expression (I) is exponential. Thus, without these considerations the quantitative applicability of earlier expressions is questionable. By examining the variation in T_m^N with c_m for a single N, all assumptions, required for evaluating V_r^f or the entropic effects of discontinuities in the (A)_N strand are avoided in the determination of a reliable enthalpy. We have therefore examined the system ((III)) and obtained a ΔH_r = 12.58 ± 0.08 kcal per mole (A)·2(U) base-triplets between 5 and 2.5°C. That this value for ΔH_r is in such excellent agreement with all calorimetric values reported for (A)∞·2(U)∞ suggests that the enthalpy for reaction(III) is not significantly affected by disconnections in the backbone of (A)₄·2(U)∞. From (I), V_r^f = 6.0 × 10^?4 1/mole or 1 Å ³per helical residue. ΔH_r°, corrected for residual single-strand stacking in (A)₄, is in excellent agreement with that found earlier for (A)₁·2(U)∞. A residual heat capacity of 90 kcal(±20) per mole (A)·2(U) base-triplets per °C is deduced from the decrease of ΔH_r° with temperature.     

Evolution of C4 phosphoenolpyruvate carboxylase in the genus Alternanthera: gene families and the enzymatic characteristics of the C4 isozyme and its orthologues in C3 and C3/C4 Alternantheras

Phosphoenolpyruvate carboxylase (PEPCase, EC 4.1.1.3) is a key enzyme of C₄ photosynthesis. It has evolved from ancestral non-photosynthetic (C₃) isoforms and thereby changed its kinetic and regulatory properties. We are interested in understanding the molecular changes, as the C₄ PEPCases were adapted to their new function in C₄ photosynthesis and have therefore analysed the PEPCase genes of various Alternanthera species. We isolated PEPCase cDNAs from the C₄ plant Alternanthera pungens H.B.K., the C₃/C₄ intermediate plant A. tenella Colla, and the C₃ plant A. sessilis (L.) R.Br. and investigated the kinetic properties of the corresponding recombinant PEPCase proteins and their phylogenetic relationships. The three PEPCases are most likely derived from orthologous gene classes named ppcA. The affinity constant for the substrate phosphoenolpyruvate (K _0.5 PEP) and the degree of activation by glucose-6-phosphate classified the enzyme from A. pungens (C₄) as a C₄ PEPCase isoform. In contrast, both the PEPCases from A. sessilis (C₃) and A. tenella (C₃/C₄) were found to be typical C₃ PEPCase isozymes. The C₄ characteristics of the PEPCase of A. pungens were accompanied by the presence of the C₄-invariant serine residue at position 775 reinforcing that a serine at this position is essential for being a C₄ PEPCase (Svensson et al. 2003). Genomic Southern blot experiments and sequence analysis of the 3′ untranslated regions of these genes indicated the existence of PEPCase multigene family in all three plants which can be grouped into three classes named ppcA, ppcB and ppcC.     

A comparison of the attraction of nymphs and adults of the ticksAmblyomma hebraeum andA. variegatum to carbon dioxide and the male-produced aggregation-attachment pheromone

The attraction of nymphs of the ticksAmblyomma hebraeum andA. variegatum to CO₂ alone and CO₂ together with the male-produced aggregation-attachment pheromone (AAP) was investigated. Matching experiments on the attraction of the adults of the two species were run for comparison. Nymphs ofA. hebraeum were strongly attracted to sources of CO₂ and CO₂/AAP at distances of 10 and 15 m. At distances of 20 and 25 m significantly more nymphs were attracted to CO₂/AAP than to CO₂ alone. Adults ofA. hebraeum were not attracted to CO₂ alone at any distance; these ticks were attracted to CO₂ and AAP together for distances of up to 25 m. The patterns of attraction of nymphs and adults ofA. variegatum at 10 m were similar to those recorded inA. hebraeum.     

Application of thin film dialysis to the determination of equilibrium constants

A theoretical basis for thin-film dialysis involving binding between a ligand and nondialyzing species is presented. A general differential equation that applies to the case of equivalent, noninteracting sites is derived relating [A]_F, [A]_T, [P]_T, and K. Numerical solutions to this equation are used to develop a series of escape curves corresponding to specific values of the parameters [P]_T, [A]_i, K, and k₀. A general method for determining an equilibrium binding constant from thin-film dialysis data is given. A comparison of thin-film dialysis results predicted by this theory with literature data shows essential agreement.     

Characterization of two methylenedioxy bridge-forming cytochrome P450-dependent enzymes of alkaloid formation in the Mexican prickly poppy Argemone mexicana

Formation of the methylenedioxy bridge is an integral step in the biosynthesis of benzo[c]phenanthridine and protoberberine alkaloids in the Papaveraceae family of plants. This reaction in plants is catalyzed by cytochrome P450-dependent enzymes. Two cDNAs that encode cytochrome P450 enzymes belonging to the CYP719 family were identified upon interrogation of an EST dataset prepared from 2-month-old plantlets of the Mexican prickly poppy Argemone mexicana that accumulated the benzo[c]phenanthridine alkaloid sanguinarine and the protoberberine alkaloid berberine. CYP719A13 and CYP719A14 are 58% identical to each other and 77% and 60% identical, respectively, to stylopine synthase CYP719A2 of benzo[c]phenanthridine biosynthesis in Eschscholzia californica. Functional heterologous expression of CYP719A14 and CYP719A13 in Spodoptera frugiperda Sf9 cells produced recombinant enzymes that catalyzed the formation of the methylenedioxy bridge of (S)-cheilanthifoline from (S)-scoulerine and of (S)-stylopine from (S)-cheilanthifoline, respectively. Twenty-seven potential substrates were tested with each enzyme. Whereas CYP719A14 transformed only (S)-scoulerine to (S)-cheilanthifoline (K_m 1.9 ± 0.3; k_cat/K_m 1.7), CYP719A13 converted (S)-tetrahydrocolumbamine to (S)-canadine (K_m 2.7 ± 1.3; k_cat/K_m 12.8), (S)-cheilanthifoline to (S)-stylopine (K_m 5.2 ± 3.0; k_cat/K_m 2.6) and (S)-scoulerine to (S)-nandinine (K_m 8.1 ± 1.9; k_cat/K_m 0.7). These results indicate that although CYP719A14 participates in only sanguinarine biosynthesis, CYP719A13 can be involved in both sanguinarine and berberine formation in A. mexicana.     

Evolution of pseudogenes in the immunoglobulin V H-gene family of the mouse

A quantitative analysis of the complexity of the J558 V _H -gene family in the mouse immunoglobulin heavy chain (Igh) gene locus has been performed. Considerable variations in the degree of complexity are observed in various Igh haplotypes derived from laboratory mice and wild mice. The BALB/c strain shows the highest degree of complexity of the J558 V _H -gene family when all mice are compared. Multiple gene duplications seem to have occurred in the BALB/c-derived J558 V_H-gene family less than 1–2 million years ago. This dating is supported by the divergence in coding and flanking regions of three strongly homologous V _H -region genes. Two of these genes were generated by the duplication of a pseudogene about 1.5 × 10⁵ years ago. A recent expansion of the J558 V _H -gene family and therefore little time for evolutionary drift may explain why most of the pseudogenes in this family exhibit a largely intact structure. We also describe two V _H -region genes which represent older pseudogenes in states of progressive disintegration.     

Kinetics of the effect of amiloride on the permeability of the apical membrane of rabbit descending colon to sodium

Summary The effects of the addition of graded concentrations of amiloride, (A) _m , to the mucosal bathing solution on the permeability of the apical membrane of rabbit descending colon to Na (P _Na ^m ) were determined when the Na activity in the mucosal bathing solution, (Na) _m , was 18, 32 or 100mm.P _Na ^m was obtained from current-voltage relations determined on tissues bathed with a high-K serosal solution before and after the addition of a maximally inhibitory concentration of amiloride to the mucosal solution as described by Turnheim et al. (Turnheim, K., Thompson, S.M., Schultz. S.G. 1983.J. Membrane Biol. 76:299–309).The results indicate that: (1) As demonstrated previously (Turnheim et al., 1983),P _Na ^m decreases with increasing (Na) _m . (2)P _Na ^m also decreases hyperbolically with increasing (A) _m . Kinetic analyses of the effect of amiloride onP _Na ^m are consistent with the conclusions that: (i) the stoichiometry between the interaction of amiloride with apical membrane receptors that results in a decrease inP _Na ^m is one-for-one; (ii) there is no evidence for cooperativity between amiloride and these binding sites; (iii) the value of (A) _m needed to halveP _Na ^m at a fixed (Na) _m is 0.6–1.0 m; and, (iv) this value is independent of (Na) _m over the fivefold range studied.These findings are consistent with the notion that the sites with which amiloride interacts to bring about closure of the channels through which Na crosses the apical membrane arekinetically distinct from the sites with which (Na) _m interacts to bring about closure (i.e., self-inhibition). In short, the effects of (Na) _m and (A) _m onP _Na ^m in this tissue appear to be independent and additive.     

Studies on the ability of mycotoxins to diffuse in bread

Summary The moulds Aspergillus parasiticus (aflatoxins B₁, B₂, G₁, G₂, and M₁), A. ochraceus (ochratoxin A) and Penicillium chrysogenum (citrinin) were grown on whole wheat bread either in the presence or absence of oxygen. In the presence of oxygen, both A. parasiticus and A. ochraceus developed dense colonies and formed considerable amounts of mycotoxins whereas Penicillium chrysogenum only grew and produced citrinin on the surface of the bread. In the absence of oxygen fungal growth did not occur and most of the toxins were undetectable even in regions of bread immediately adjacent to the moulds although a very slight diffusion of the aflatoxins B₁ and G₁ through 1 cm was observed. It is concluded that diffusion of the tested mycotoxins from hyphae into bread is not a problem for food safety.     

Involvement of a plasmid in the hairy root disease of plants caused by Agrobacterium rhizogenes

Agrobacterium rhizogenes causes a proliferation of roots on plants that it infects. This is in contrast to Agrobacterium tumefaciens which causes gall or tumor formation on its hosts. A large molecular weight plasmid (1.1 × 10⁸) in A. rhizogenes strain A₄ is correlated with the infectivity of this organism. However, this plasmid apparently carries additional information not vital to the infection process. Experimental evidence supporting these conclusions is: (i) A. rhizogenes A₄loses infectivity when all or part of the plasmid is lost after treatment with ethidium bromide or after heating at 37 °C. (ii) There occurs successful conjugational transfer of the A₄ plasmid in planta to a noninfectious, antibiotic-resistant A. radiobacter. Infectious transconjugants were antibiotic resistant and contain a plasmid comparable to that of A. rhizogenes A₄. (iii) A. rhizogenes A₄ and the transconjugants possessed identical EcoR1 restriction endonuclease patterns, whereas three ethidium bromide-treated isolates that were noninfectious but plasmid containing had lost or gained bands in the pattern. The infectious plasmid of A. rhizogenes A₄ has been designated pHrA₄. Some potential benefits of the A. rhizogenes plasmid to agriculture are discussed.     

Operation of the cbb3-type terminal oxidase in Azotobacter vinelandii

A part of the gene encoding cbb ₃-type cytochrome oxidase CcoN subunit was cloned from Azotobacter vinelandii and a mutant strain of this bacterium with disrupted ccoN gene was constructed. In contrast to the wild type strain, this one is unable to oxidize cytochromes c ₄ and c ₅. Thus, the A. vinelandii respiratory chain is shown to contain cbb ₃-type cytochrome c oxidase. It is also shown that the activity of this enzyme is not necessary for diazotrophic growth of A. vinelandii at high oxygen concentrations.     

Assignment of the histidine 12-threonine 45 hydrogen-bonded proton in the NMR spectrum of ribonuclease A in H2O.

Described herein are proton nmr experiments on chemically modified derivatives of ribonuclease A designed to elucidate the origin of an exchangeable resonance, assigned previously to a histidine ring N proton that titrates between 11 to 13 ppm with a pK_a of 6.1 in H₂O solution. Histidines 48 and 105, which are distant from the active site, are eliminated as candidates for this resonance from inhibitor binding studies on the enzyme in acetate–water solutions. This exchangeable resonance titrates with modified pK_a's and constant area over the above pH range in His-119-N₁-carboxymethylated-RNase A and des-(121–124)-RNase A, thus eliminating the imidazole N₃ proton in the His 119-Asp 121 hydrogen bond. In His-12-N₁-carboxymethylated-RNase A, this resonance is also observable, but broadens on raising the pH above 7 and at elevated temperatures above neutrality. It exhibits a pH-independent chemical shift characteristic of the protonated state of histidine. On the basis of these findings, this exchangeable resonance, designated a, is assigned to the imidazole N₁ proton of His 12, which is hydrogen-bonded to the carbonyl oxygen of Thr 45 in the crystal.     

Molecular and functional analysis of the lipopolysaccharide biosynthesis locus wlb from Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica

The Bordetella pertussis wlb locus (wlb_pe, formerly bpl ) is required for the biosynthesis of a trisaccharide that, when attached to the B. pertussis lipopolysaccharide (LPS) core (band B), generates band A LPS. The equivalent loci in Bordetella bronchiseptica (wlb_br) and Bordetella parapertussis (wlb_pa) were identified and cloned. The wlb_br and wlb_pa loci differ from wlb_pe in that they lack the insertion sequence that defines the right-hand terminus of wlb_pe. Deletion of 12 kb of DNA containing the whole wlb locus (Δwlb) by allelic exchange in each of the three bordetellae had no effect on band B biosynthesis, whereas band A biosynthesis was prevented in B. pertussis and B. bronchiseptica. In B. bronchiseptica and B. parapertussis, Δwlb mutants also lacked O-antigen. Reintroduction of the wlb_pe or wlb_br loci on a shuttle vector into the three Δwlb mutants restored the wild-type LPS phenotype in the B. pertussis and B. bronchiseptica mutants. In the case of B. parapertussis, which normally does not synthesize an apparent band A structure, introduction of the wlb_pe or wlb_br loci now enabled the generation of band A. This suggests that the attachment point for band A trisaccharide on the LPS core is present in B. parapertussis, and further suggests that the wild-type wlb_pa locus is not fully functional. Introduction of the wlb_pa locus into the Δwlb_pe, Δwlb_br and Δwlb_pa mutants had interesting consequences. The B. bronchiseptica and B. parapertussis recipients were now able to biosynthesize O-antigen, but no band A was generated. In the B. pertussis recipient, a truncated band A was expressed consistent with a mutation in the wlbH gene, but on Western blotting the expression of a small amount of full-length band A was also seen. Evidence that the wlbH_pa protein is not fully functional was provided by the failure of the wlb_pa locus to fully complement a B. pertussis wlbH (ΔwlbH_pe) mutant. This was supported by DNA sequence data showing that a single amino acid, conserved between homologous proteins from a range of bacteria, is altered in the B. parapertussis WlbH protein.     

Evaluation of the mycological status of luncheon meat with special reference to aflatoxigenic moulds and aflatoxin residues

The luncheon meat samples analyzed, which were produced locally by the two main luncheon meat producing companies in Egypt were relatively highly contaminated either by moulds and yeasts in general, aflatoxigenic species and aflatoxin residues in particular. The most frequently encountered fungi from the samples were yeasts, Aspergillus niger, A. flavus, Penicillium chrysogenum, Rhizopus stolonifer, Mucor circinelloides. Less common were Cladosporium sphaerospermum, Alternaria alternata, Mycosphaerella tassiana, P. aurantiogriseum and P. oxalicum. The most important aflatoxigenic species, A. flavus, was isolated frequently. It was 10% of the total fungal isolates from both samples of the two companies. Seven luncheon meat samples out of 50 analyzed were positive for aflatoxin B₁ or B₁ and G₁, while all samples were negative for aflatoxins B₂, G₂, M₁ and M₂. Aflatoxin B₁ was detected only in 4 and 3 samples out of 25 analyzed from each of company A and B, respectively. The highest detectable level, 11.1 ppb, was recorded in a sample from company B and the least, 0.5 ppb, in a sample from company A. Aflatoxin G₁, at concentration of 3.2 ppb, was detected in only one sample of the aflatoxin B₁ – contaminated 3 samples of company B: this sample also had the highest level of aflatoxin B₁. Some luncheon meat samples had higher numbers of aflatoxigenic A. flavus than others, however these samples were negative for aflatoxins. The hazardous potential of such contamination will be discussed. This revised version was published online in June 2006 with corrections to the Cover Date.