Aflatoxin B1 effect on enzyme biosynthesis in Bacillus cereus and Bacillus licheniformis

1970 ◽  
Vol 16 (11) ◽  
pp. 1059-1065 ◽  
Author(s):  
Eivind B. Lillehoj ◽  
Alex Ciegler

The effect of aflatoxin B1 on induced and constitutive enzyme synthesis was examined in strains of Bacillus cereus (NRRL B-569, NRRL B-3537) and Bacillus licheniformis (NRRL B-3560, NRRL B-3540). Although B1 partially blocked penicillinase elaboration in B. cereus after incubation with the toxin, the level of B1-mediated reduction in total protein synthesis was similar to the diminished production of penicillinase. Comparative studies on the effects of aflatoxin B1 and actinomycin D on enzyme synthesis and growth in B. licheniformis demonstrated that actinomycin D exerted a differential inhibitory effect on induction of penicillinase and α-glucosidase, whereas levels of reduction of enzyme production initiated by aflatoxin resembled toxin-mediated growth inhibition. Thus, the mode of action of aflatoxin B1 is not exclusively analogous to that of actinomycin D in B. licheniformis. However, induced-penicillinase production in B. licheniformis was enhanced by relatively low levels of both actinomycin D and aflatoxin B1.

1968 ◽  
Vol 108 (4) ◽  
pp. 675-677 ◽  
Author(s):  
M D Yudkin

1. Previous studies of penicillinase synthesis in Bacillus licheniformis showed that enzyme synthesis after the addition of actinomycin continues for far longer in the constitutive mutant 749/C than in the parental inducible strain (Yudkin, 1966). This result was interpreted as indicating a difference in the lifetime of specific messenger RNA in the two strains. Other bacilli have now been examined in an attempt to see whether this difference is general. 2. There was no difference in the lifetime of messenger RNA for penicillinase synthesis between an inducible and a constitutive strain of Bacillus cereus. 3. Three freshly isolated constitutive mutants of B. licheniformis also had short-lived messenger RNA, like their inducible parent. 4. A reinvestigation of mutant 749/C confirmed the original finding that, on treatment with actinomycin, it continued to synthesize penicillinase far longer than did its parent. 5. An inducible revertant of mutant 749/C was indistinguishable from the original inducible strain, and appeared to have lost both constitutivity and long-lived messenger RNA in the back mutation.


PEDIATRICS ◽  
1966 ◽  
Vol 38 (1) ◽  
pp. 111-121 ◽  
Author(s):  
Shimon W. Moses ◽  
Stanley Levin ◽  
Reuben Chayoth ◽  
Kurt Steinitz

In cases of glycogen storage disease Type III, low levels of liver glucose-6-phosphatase activity have frequently been found in addition to the complete absence of amylo-l, 6-glucosidase activity. Glucose-6-phosphatase regulates a key reaction in the homeostatic control of gluconeogenesis. It belongs to the group of adaptive enzymes, and it has been shown in rats that its activity can be induced by steroids and suppressed by insulin. Increasing evidence is accumulating to indicate that the hormonal control of this enzyme activity affects de novo synthesis at the gene level. The subnormal activity of glucose-6-phosphatase in cases of amylo-1, 6-glucosidase deficiency could be the result of a double enzyme deficiency due to two structural gene defects, or secondary to a regulatory gene disorder resulting in suppression of glucose-6-phosphatase biosynthesis. If the low levels of glucose-6-phosphatase activity result from a structural gene mutation, hormonal induction of enzyme biosynthesis would be unlikely; whereas, if the markedly depressed activity of this enzyme is due to abnormal control affecting the regulation of enzyme synthesis, hormonal induction may be possible. A case of amylo-1, 6-glucosidase type A is presented in which, in addition to complete absence of the debrancher enzyme, exceedingly low values of liver glucose-6-phosphatase were repeatedly demonstrated. Low insulin-like activity was found in the patient's plasma, but no significant abnormality of steroid metabolism could be shown. Triamcinolone administration resulted in fourfold increase of liver glucose-6-phosphatase activity. This enzyme induction by Triamcinolone suggests that the markedly reduced levels of glucose-6-phosphatase activity prior to steroid administration were due to a regulatory disorder of enzyme biosynthesis and not to a structural gene defect. It is suggested that the Triamcinolone induction test can be used in similar situations as a diagnostic tool to differentiate between a regulatory gene disorder affecting enzyme synthesis, and a structural gene defect.


1968 ◽  
Vol 57 (3_Suppl) ◽  
pp. S19-S35 ◽  
Author(s):  
Å. Hjalmarson

ABSTRACT In vitro addition of bovine growth hormone (GH) to intact hemidiaphragms from hypophysectomized rats has previously been found to produce both an early stimulatory effect lasting for 2—3 hours and a subsequent late inhibitory effect during which the muscle is insensitive to further addition of GH (Hjalmarson 1968). These effects on the accumulation rate of α-aminoisobutyric acid (AIB) and D-xylose have been further studied. In presence of actinomycin D (20 μg/ml) or puromycin (100 μg/ml) the duration of the stimulatory effect of GH (25 μg/ml) was prolonged to last for at least 4—5 hours and the late inhibitory effect was prevented. Similar results were obtained when glucose-free incubation medium was used. Preincubation of the diaphragm at different glucose concentrations (0—5 mg/ml) for 3 hours did not change the GH sensitivity. Addition of insulin at start of incubation could not prevent GH from inducing its late inhibitory effect, while dexamethasone seemed to potentiate this effect of GH. Furthermore, adrenaline was found to decrease the uptake of AIB-14C and D-xylose-14C in the diaphragm, but not to change the sensitivity of the muscle to GH. Preincubation of the diaphragm for 3 hours with puromycin in a concentration of 200 μg/ml markedly decreased the subsequent basal uptake of both AIB-14C and D-xylose-14C, in the presence of puromycin, and abolished the stimulatory effect of GH on the accumulation of AIB-14C. However, the effect of GH on the accumulation of D-xylose-14C was unchanged. The present observations are discussed and evaluated in relation to various mechanisms of GH action proposed to explain the dual nature of the hormone.


2019 ◽  
Vol 17 ◽  
Author(s):  
Farzane Kargar ◽  
Mojtaba Mortazavi ◽  
Mahmood Maleki ◽  
Masoud Torkzadeh Mahani ◽  
Younes Ghasemi ◽  
...  

Aims: The purpose of this study was to screen the bacteria producing cellulase enzymes and their bioinformatics studies. Background: Cellulose is a long-chain polymer of glucose that hydrolyzes by cellulases to glucose molecules. In order to design the new biotechnological applications, some strategies have been used as increasing the efficiency of enzyme production, generating cost-effective enzymes, producing stable enzymes and identification of new strains. Objective: On the other hand, some bacteria special features have made them suitable candidates for the identification of the new source of enzymes. In this regard, some native strains of bacteria were screened. Method: These bacteria were grown on a culture containing the liquid M9 media containing CMC to ensure the synthesis of cellulase. The formation of a clear area in the culture medium indicated decomposition of cellulose. In the following, the DNA of these bacteria were extracted and their 16S rDNA genes were amplified. Result: The results show that nine samples were able to synthesize cellulase. In following, these strains were identified using 16S rDNA. The results show that these screened bacteria belonged to the Bacillus sp., Alcaligenes sp., Alcaligenes sp., and Enterobacter sp.conclusionThe enzyme activity analysis shows that the Bacillus toyonensis, Bacillus sp. strain XA15-411 Bacillus cereus have produced the maximum yield of cellulases. However, these amounts of enzyme production in these samples are not proportional to their growth rate. As the bacterial growth chart within 4 consecutive days shows that the Alcaligenes sp. Bacillus cereus, Bacillus toyonensis, Bacillus sp. strain XA15-411 have a maximum growth rate. The study of the phylogenetic tree also shows that Bacillus species are more abundant in the production of cellulase enzyme. These bioinformatics analyses show that the Bacillus species have different evolutionary relationships and evolved in different evolutionary time. Other: However, for maximum cellulase production by this bacteria, some information as optimum temperature, optimum pH, carbon and nitrogen sources are needed for the ideal formulation of media composition. The cellulase production is closely controlled in microorganisms and the cellulase yields appear to depend on a variety of factors. However, the further studies are needed for cloning, purification and application of these new microbial cellulases in the different commercial fields as in food, detergent, and pharmaceutical, paper, textile industries and also various chemical industries. However, these novel enzymes can be further engineered through rational design or using random mutagenesis techniques.


2013 ◽  
Vol 305 (9) ◽  
pp. F1365-F1373 ◽  
Author(s):  
Ling Yu ◽  
Otor Al-Khalili ◽  
Billie Jeanne Duke ◽  
James D. Stockand ◽  
Douglas C. Eaton ◽  
...  

Epithelial Na+ channel (ENaC) activity, which determines the rate of renal Na+ reabsorption, can be regulated by G protein-coupled receptors. Regulation of ENaC by Gα-mediated downstream effectors has been studied extensively, but the effect of Gβγ dimers on ENaC is unclear. A6 cells endogenously contain high levels of Gβ1 but low levels of Gβ3, Gβ4, and Gβ5 were detected by Q-PCR. We tested Gγ2 combined individually with Gβ1 through Gβ5 expressed in A6 cells, after which we recorded single-channel ENaC activity. Among the five β and γ2 combinations, β1γ2 strongly inhibits ENaC activity by reducing both ENaC channel number ( N) and open probability ( Po) compared with control cells. In contrast, the other four β-isoforms combined with γ2 have no significant effect on ENaC activity. By using various inhibitors to probe Gβ1γ2 effects on ENaC regulation, we found that Gβ1γ2-mediated ENaC inhibition involved activation of phospholipase C-β and its enzymatic products that induce protein kinase C and ERK1/2 signaling pathways.


1991 ◽  
Vol 173 (6) ◽  
pp. 1305-1310 ◽  
Author(s):  
M Gadina ◽  
R Bertini ◽  
M Mengozzi ◽  
M Zandalasini ◽  
A Mantovani ◽  
...  

The present study was designed to define the potential of chlorpromazine (CPZ) as a protective agent against lipopolysaccharide (LPS) toxicity in comparison with glucocorticoids, and to obtain initial correlations with its effects on the levels of tumor necrosis factor (TNF), a pivotal mediator of endotoxic shock. It was found that CPZ protects mice, normal or adrenalectomized, and guinea pigs against lethality of LPS, and inhibited TNF serum levels, like dexamethasone (DEX), a well-known inhibitor of TNF synthesis. CPZ protected against LPS lethality when administered 30 minutes (min) before, simultaneously, or up to 10 min after LPS and was ineffective when given 30 min after LPS, paralleling the inhibitory effect on TNF production. In another experimental model, where mice were sensitized to LPS toxicity by actinomycin D, CPZ significantly inhibited LPS lethality and hepatotoxicity, whereas under these conditions DEX was inactive. These experiments indicate that CPZ has a protective action in both glucocorticoid-sensitive and -resistant models of endotoxic shock.


2006 ◽  
Vol 290 (1) ◽  
pp. C143-C151 ◽  
Author(s):  
Y. Osawa ◽  
H. T. Lee ◽  
C. A. Hirshman ◽  
D. Xu ◽  
C. W. Emala

LPS is known to modulate macrophage responses during sepsis, including cytokine release, phagocytosis, and proliferation. Although agents that elevate cAMP reverse LPS-induced macrophage functions, whether LPS itself modulates cAMP and whether LPS-induced decreases in proliferation are modulated via a cAMP-dependent pathway are not known. Murine macrophages (RAW264.7 cells) were treated with LPS in the presence or absence of inhibitors of prostaglandin signaling, protein kinases, CaM, Giproteins, and NF-κB translocation or transcription/translation. LPS effects on CaMKII phosphorylation and the expression of relevant adenylyl cyclase (AC) isoforms were measured. LPS caused a significant dose (5–10,000 ng/ml)- and time (1–8 h)-dependent increase in forskolin-stimulated AC activity that was abrogated by pretreatment with SN50 (an NF-κB inhibitor), actinomycin D, or cycloheximide, indicating that the effect is mediated via NF-κB-dependent transcription and new protein synthesis. Furthermore, LPS decreased the phosphorylation state of CaMKII, and pretreatment with a CaM antagonist attenuated the LPS-induced sensitization of AC. LPS, cAMP, or PKA activation each independently decreased macrophage proliferation. However, inhibition of NF-κB had no effect on LPS-induced decreased proliferation, indicating that LPS-induced decreased macrophage proliferation can proceed via PKA-independent signaling pathways. Taken together, these findings indicate that LPS induces sensitization of AC activity by augmenting the stimulatory effect of CaM and attenuating the inhibitory effect of CaMKII on isoforms of AC that are CaMK sensitive.


2009 ◽  
Vol 2 (3) ◽  
pp. 305-312 ◽  
Author(s):  
A. Nesci ◽  
S. Marín ◽  
M. Etcheverry ◽  
V. Sanchis

This research was undertaken to evaluate the effects of the natural phytochemicals trans-cinnamic acid (CA) alone at concentrations of 20 and 25 mM, ferulic acid (FA) at concentration of 30 mM and two mixtures, CA-FA (20+30 mM) and CA-FA (25+30 mM) on natural maize mycoflora, Aspergillus section Flavi population and aflatoxin B1 production. These studies were carried out in maize grain in relation to a water activity of 0.99, 0.97 and 0.94. CA at 25 mM and the mixture CA-FA (25+30 mM) were the most effective treatments at inhibiting natural maize mycoflora at all aw assayed after 11 and 35 days of incubation at 25 °C. In general, 20 mM CA caused complete inhibition of Aspergillus section Flavi population at all aw values tested during all incubation period without an additional inoculum. 20 mM CA and 25 mM CA showed the major inhibitory effect on aflatoxin B1 accumulation of control and Aspergillus section Flavi additionally inoculated during all incubation periods. The data showed that CA and FA could be considered as effective fungitoxicants for natural maize mycoflora and aflatoxigenic fungi in the aw range 0.99 to 0.94. The information obtained shows promise for controlling aflatoxigenic fungi in stored maize.


2008 ◽  
Vol 54 (4) ◽  
pp. 321-325 ◽  
Author(s):  
Monique Haakensen ◽  
Barry Ziola

An ATP-binding cassette (ABC) multi-drug resistance (MDR) gene was found in 4 Gram-positive bacterial isolates of environmental origin and found capable of spoiling beer. The bacteria isolated were Bacillus cereus , Bacillus licheniformis , Paenibacillus humicus , and Staphylococcus epidermidis ; all of which were previously unappreciated as beer-spoilage bacteria. The MDR gene found in these bacteria has less than 37% similarity to known ABC MDR proteins described for Bacillus and Staphylococcus , and this is the first finding of an ABC MDR gene in the genus Paenibacillus . The sequenced region of the gene was translated and compared phylogenetically with the closest GenBank matches of the respective species and the closest GenBank matches overall. The ABC MDR proteins from these isolates were found to cluster among known sequences of HorA, sharing 99.5% identity within the sequenced region. In the beer-spoilage-associated genera Lactobacillus and Pediococcus , the presence of the MDR gene horA correlates with the ability to grow in beer. As the unique horA-harbouring isolates described here are capable of growing in beer, it is likely that the presence of the horA gene likewise confers hop resistance to these organisms.


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