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Archives of Microbiology (v.184, #1)
Topological and transcriptional analysis of pssL gene product: a putative Wzx-like exopolysaccharide translocase in Rhizobium leguminosarum bv. trifolii TA1 by Andrzej Mazur; Małgorzata Marczak; Jarosław E. Król; Anna Skorupska (pp. 1-10).
An identified pssL gene is yet another one, besides the pssT, pssN and pssP genes, encoding for a protein engaged in polysaccharide polymerization and export in Rhizobium leguminosarum bv. trifolii strain TA1 (RtTA1). Amino acid sequence similarity and hypothetical protein secondary structure placed the PssL protein within Wzx (RfbX) translocases with putative flippase function that belong to the polysaccharide specific transport (PST) family. The predicted secondary structure of the PssL membrane protein was examined with a series of PssL–PhoA and PssL–LacZ translational fusions. The results support the hypothesis of PssL being a member of PST protein family comprising transporters with 12 membrane spanning segments and amino and carboxyl termini located in the cytoplasm. Results of semi-quantitative RT-PCR showed that the initial abundance of mRNA encoding PssL protein was relatively lower when compared to the quantity of the previously identified PssT membrane protein. PssL might be a good candidate for Wzx-like protein that together with PssT (Wzy protein) could be responsible for Wzx/Wzy-like-dependent EPS polymerization and translocation in RtTA1.
Keywords: Rhizobium leguminosarum ; Exopolysaccharide translocase; Membrane topology
Topological and transcriptional analysis of pssL gene product: a putative Wzx-like exopolysaccharide translocase in Rhizobium leguminosarum bv. trifolii TA1 by Andrzej Mazur; Małgorzata Marczak; Jarosław E. Król; Anna Skorupska (pp. 1-10).
An identified pssL gene is yet another one, besides the pssT, pssN and pssP genes, encoding for a protein engaged in polysaccharide polymerization and export in Rhizobium leguminosarum bv. trifolii strain TA1 (RtTA1). Amino acid sequence similarity and hypothetical protein secondary structure placed the PssL protein within Wzx (RfbX) translocases with putative flippase function that belong to the polysaccharide specific transport (PST) family. The predicted secondary structure of the PssL membrane protein was examined with a series of PssL–PhoA and PssL–LacZ translational fusions. The results support the hypothesis of PssL being a member of PST protein family comprising transporters with 12 membrane spanning segments and amino and carboxyl termini located in the cytoplasm. Results of semi-quantitative RT-PCR showed that the initial abundance of mRNA encoding PssL protein was relatively lower when compared to the quantity of the previously identified PssT membrane protein. PssL might be a good candidate for Wzx-like protein that together with PssT (Wzy protein) could be responsible for Wzx/Wzy-like-dependent EPS polymerization and translocation in RtTA1.
Keywords: Rhizobium leguminosarum ; Exopolysaccharide translocase; Membrane topology
Transcriptional response reveals translation machinery as target for high pressure in Lactobacillus sanfranciscensis by Melanie Pavlovic; Sebastian Hörmann; Rudi F. Vogel; Matthias A. Ehrmann (pp. 11-17).
The effect of sublethal hydrostatic pressure on the transcriptome of Lactobacillus sanfranciscensis was determined using a shot-gun-microarray. Among the 750 spots that passed quality analysis 42 genes were induced, while six were repressed when cells were incubated at 45 MPa for 30 min. The nature of genes and their differential expression clearly indicate cellular efforts to counteract a decrease in translational capacity. The majority of high pressure affected genes were found to encode either translation factors (EF-G, EF-TU), ribosomal proteins (S2, L6, L11), genes changing translational accuracy or molecular chaperones (GroEL, ClpL). These data agree with previously reported effects observed in in vitro studies as well as with physiological and proteomic data. This study provides in vivo evidence to identify ribosomes and impaired translation among primary targets for high pressure treatment. The observed induction of heat as well as cold shock genes (e.g. hsp60, gyrA) may be explained as a result of high pressure affected protein synthesis.
Keywords: High hydrostatic pressure; Stress response; Lactic acid bacteria; Lactobacillus sanfranciscensis ; Transcriptome
Transcriptional response reveals translation machinery as target for high pressure in Lactobacillus sanfranciscensis by Melanie Pavlovic; Sebastian Hörmann; Rudi F. Vogel; Matthias A. Ehrmann (pp. 11-17).
The effect of sublethal hydrostatic pressure on the transcriptome of Lactobacillus sanfranciscensis was determined using a shot-gun-microarray. Among the 750 spots that passed quality analysis 42 genes were induced, while six were repressed when cells were incubated at 45 MPa for 30 min. The nature of genes and their differential expression clearly indicate cellular efforts to counteract a decrease in translational capacity. The majority of high pressure affected genes were found to encode either translation factors (EF-G, EF-TU), ribosomal proteins (S2, L6, L11), genes changing translational accuracy or molecular chaperones (GroEL, ClpL). These data agree with previously reported effects observed in in vitro studies as well as with physiological and proteomic data. This study provides in vivo evidence to identify ribosomes and impaired translation among primary targets for high pressure treatment. The observed induction of heat as well as cold shock genes (e.g. hsp60, gyrA) may be explained as a result of high pressure affected protein synthesis.
Keywords: High hydrostatic pressure; Stress response; Lactic acid bacteria; Lactobacillus sanfranciscensis ; Transcriptome
The activity of ribosome modulation factor during growth of Escherichia coli under acidic conditions by Walid M. El-Sharoud; Gordon W. Niven (pp. 18-24).
Expression of the gene encoding ribosome modulation factor (RMF), as measured using an rmf-lacZ gene fusion, increased with decreasing pH in exponential phase cultures of Escherichia coli. Expression was inversely proportional to the growth rate and independent of the acidifying agent used and it was concluded that expression of rmf was growth rate controlled in exponential phase under acid conditions. Increased rmf expression during exponential phase was not accompanied by the formation of ribosome dimers as occurs during stationary phase. Nor did it appear to have a significant effect on cell survival under acid stress since the vulnerability of an RMF-deficient mutant strain was similar to that of the parent strain. Ribosome degradation was increased in the mutant strain compared to the parent strain at pH 3.75. Also, the peptide elongation rate was reduced in the mutant strain but not the parent during growth under acid conditions. It is speculated that the function of RMF during stress-induced reduction in growth rate is two-fold: firstly to prevent reduced elongation efficiency by inactivating surplus ribosomes and thus limiting competition for available protein synthesis factors, and secondly to protect inactivated ribosomes from degradation.
Keywords: Ribosome modulation factor; RMF; Acid stress; Ribosome dimerisation
The activity of ribosome modulation factor during growth of Escherichia coli under acidic conditions by Walid M. El-Sharoud; Gordon W. Niven (pp. 18-24).
Expression of the gene encoding ribosome modulation factor (RMF), as measured using an rmf-lacZ gene fusion, increased with decreasing pH in exponential phase cultures of Escherichia coli. Expression was inversely proportional to the growth rate and independent of the acidifying agent used and it was concluded that expression of rmf was growth rate controlled in exponential phase under acid conditions. Increased rmf expression during exponential phase was not accompanied by the formation of ribosome dimers as occurs during stationary phase. Nor did it appear to have a significant effect on cell survival under acid stress since the vulnerability of an RMF-deficient mutant strain was similar to that of the parent strain. Ribosome degradation was increased in the mutant strain compared to the parent strain at pH 3.75. Also, the peptide elongation rate was reduced in the mutant strain but not the parent during growth under acid conditions. It is speculated that the function of RMF during stress-induced reduction in growth rate is two-fold: firstly to prevent reduced elongation efficiency by inactivating surplus ribosomes and thus limiting competition for available protein synthesis factors, and secondly to protect inactivated ribosomes from degradation.
Keywords: Ribosome modulation factor; RMF; Acid stress; Ribosome dimerisation
Biodegradation of dipropyl phthalate and toxicity of its degradation products: a comparison of Fusarium oxysporum f. sp. pisi cutinase and Candida cylindracea esterase by Yang-Hoon Kim; Jiho Min; Kyung-Dong Bae; Man Bock Gu; Jeewon Lee (pp. 25-31).
The efficiency of two lypolytic enzymes (fungal cutinase, yeast esterase) in the degradation of dipropyl phthalate (DPrP) was investigated. The DPrP-degradation rate of fungal cutinase was surprisingly high, i.e., almost 70% of the initial DPrP (500 mg/l) was decomposed within 2.5 h and nearly 50% of the degraded DPrP disappeared within the initial 15 min. With the yeast esterase, despite the same concentration, more than 90% of the DPrP remained even after 3 days of treatment. During the enzymatic degradation of DPrP, several DPrP-derived compounds were detected and time-course changes in composition were also monitored. The final chemical composition after 3 days was significantly dependent on the enzyme used. During degradation with fungal cutinase, most DPrP was converted into 1,3-isobenzofurandione (IBF) by diester hydrolysis. However, in the degradation by yeast esterase, propyl methyl phthalate (PrMP) was produced in abundance in addition to IBF. The toxic effects of the final degradation products were investigated using various recombinant bioluminescent bacteria. As a result, the degradation products (including PrMP) from yeast esterase severely caused oxidative stress and damage to protein synthesis in bacterial cells, while in the fungal cutinase processes, DPrP was significantly degraded to non-toxic IBF after the extended period (3 days).
Keywords: Biodegradation of dipropyl phthalate; Cutinase; Esterase; Toxicity monitoring; Recombinant bioluminescent bacteria
Biodegradation of dipropyl phthalate and toxicity of its degradation products: a comparison of Fusarium oxysporum f. sp. pisi cutinase and Candida cylindracea esterase by Yang-Hoon Kim; Jiho Min; Kyung-Dong Bae; Man Bock Gu; Jeewon Lee (pp. 25-31).
The efficiency of two lypolytic enzymes (fungal cutinase, yeast esterase) in the degradation of dipropyl phthalate (DPrP) was investigated. The DPrP-degradation rate of fungal cutinase was surprisingly high, i.e., almost 70% of the initial DPrP (500 mg/l) was decomposed within 2.5 h and nearly 50% of the degraded DPrP disappeared within the initial 15 min. With the yeast esterase, despite the same concentration, more than 90% of the DPrP remained even after 3 days of treatment. During the enzymatic degradation of DPrP, several DPrP-derived compounds were detected and time-course changes in composition were also monitored. The final chemical composition after 3 days was significantly dependent on the enzyme used. During degradation with fungal cutinase, most DPrP was converted into 1,3-isobenzofurandione (IBF) by diester hydrolysis. However, in the degradation by yeast esterase, propyl methyl phthalate (PrMP) was produced in abundance in addition to IBF. The toxic effects of the final degradation products were investigated using various recombinant bioluminescent bacteria. As a result, the degradation products (including PrMP) from yeast esterase severely caused oxidative stress and damage to protein synthesis in bacterial cells, while in the fungal cutinase processes, DPrP was significantly degraded to non-toxic IBF after the extended period (3 days).
Keywords: Biodegradation of dipropyl phthalate; Cutinase; Esterase; Toxicity monitoring; Recombinant bioluminescent bacteria
A single operon-encoded form of the acetyl-CoA decarbonylase/synthase multienzyme complex responsible for synthesis and cleavage of acetyl-CoA in Methanosarcina thermophila by David A. Grahame; Simonida Gencic; Edward DeMoll (pp. 32-40).
Methanogens growing on C-1 substrates synthesize 2-carbon acetyl groups in the form of acetyl-CoA for carbon assimilation using the multienzyme complex acetyl-CoA decarbonylase/synthase (ACDS) which contains five different subunits encoded within an operon. In species growing on acetate ACDS also functions to cleave the acetate C-C bond for energy production by methanogenesis. A number of species of Methanosarcina that are capable of growth on either C-1 compounds or acetate contain two separate ACDS operons, and questions have been raised about whether or not these operons play separate roles in acetate synthesis and cleavage. Methanosarcina thermophila genomic DNA was analyzed for the presence of two ACDS operons by PCR amplifications with different primer pairs, restriction enzyme analyses, DNA sequencing and Southern blot analyses. A single ACDS operon was identified and characterized, with no evidence for more than one. MALDI mass spectrometric analyses were carried out on ACDS preparations from methanol- and acetate-grown cells. Peptide fragmentation patterns showed that the same ACDS subunits were present regardless of growth conditions. The evidence indicates that a single form of ACDS is used both for acetate cleavage during growth on acetate and for acetate synthesis during growth on C-1 substrates.
A single operon-encoded form of the acetyl-CoA decarbonylase/synthase multienzyme complex responsible for synthesis and cleavage of acetyl-CoA in Methanosarcina thermophila by David A. Grahame; Simonida Gencic; Edward DeMoll (pp. 32-40).
Methanogens growing on C-1 substrates synthesize 2-carbon acetyl groups in the form of acetyl-CoA for carbon assimilation using the multienzyme complex acetyl-CoA decarbonylase/synthase (ACDS) which contains five different subunits encoded within an operon. In species growing on acetate ACDS also functions to cleave the acetate C-C bond for energy production by methanogenesis. A number of species of Methanosarcina that are capable of growth on either C-1 compounds or acetate contain two separate ACDS operons, and questions have been raised about whether or not these operons play separate roles in acetate synthesis and cleavage. Methanosarcina thermophila genomic DNA was analyzed for the presence of two ACDS operons by PCR amplifications with different primer pairs, restriction enzyme analyses, DNA sequencing and Southern blot analyses. A single ACDS operon was identified and characterized, with no evidence for more than one. MALDI mass spectrometric analyses were carried out on ACDS preparations from methanol- and acetate-grown cells. Peptide fragmentation patterns showed that the same ACDS subunits were present regardless of growth conditions. The evidence indicates that a single form of ACDS is used both for acetate cleavage during growth on acetate and for acetate synthesis during growth on C-1 substrates.
Formaldehyde activating enzyme (Fae) and hexulose-6-phosphate synthase (Hps) in Methanosarcina barkeri: a possible function in ribose-5-phosphate biosynthesis by Meike Goenrich; Rudolf K. Thauer; Hiroya Yurimoto; Nobuo Kato (pp. 41-48).
Formaldehyde activating enzyme (Fae) was first discovered in methylotrophic bacteria, where it is involved in the oxidation of methanol to CO2 and in formaldehyde detoxification. The 18 kDa protein catalyzes the condensation of formaldehyde with tetrahydromethanopterin (H4MPT) to methylene-H4MPT. We describe here that Fae is also present and functional in the methanogenic archaeon Methanosarcina barkeri. The faeA homologue in the genome of M. barkeri was heterologously expressed in Escherichia coli and the overproduced purified protein shown to actively catalyze the condensation reaction: apparent V max=13 U/mg protein (1 U=μmol/min); apparent Km for H4MPT=30 μM; apparent Km for formaldehyde=0.1 mM. By Western blot analysis the concentration of Fae in cell extracts of M. barkeri was determined to be in the order of 0.1% of the soluble cell proteins. Besides the faeA gene the genome of M. barkeri harbors a second gene, faeB-hpsB, which is shown to code for a 42 kDa protein with both Fae activity (3.6 U/mg) and hexulose-6-phosphate synthase (Hps) activity (4.4 U/mg). The results support the recent proposal that in methanogenic archaea Fae and Hps could have a function in ribose phosphate synthesis.
Keywords: Methanogenic archaea; Methanosarcina mazei ; C1-metabolism; Ribulose monophosphate pathway; Methanogenesis from formaldehyde
Formaldehyde activating enzyme (Fae) and hexulose-6-phosphate synthase (Hps) in Methanosarcina barkeri: a possible function in ribose-5-phosphate biosynthesis by Meike Goenrich; Rudolf K. Thauer; Hiroya Yurimoto; Nobuo Kato (pp. 41-48).
Formaldehyde activating enzyme (Fae) was first discovered in methylotrophic bacteria, where it is involved in the oxidation of methanol to CO2 and in formaldehyde detoxification. The 18 kDa protein catalyzes the condensation of formaldehyde with tetrahydromethanopterin (H4MPT) to methylene-H4MPT. We describe here that Fae is also present and functional in the methanogenic archaeon Methanosarcina barkeri. The faeA homologue in the genome of M. barkeri was heterologously expressed in Escherichia coli and the overproduced purified protein shown to actively catalyze the condensation reaction: apparent V max=13 U/mg protein (1 U=μmol/min); apparent Km for H4MPT=30 μM; apparent Km for formaldehyde=0.1 mM. By Western blot analysis the concentration of Fae in cell extracts of M. barkeri was determined to be in the order of 0.1% of the soluble cell proteins. Besides the faeA gene the genome of M. barkeri harbors a second gene, faeB-hpsB, which is shown to code for a 42 kDa protein with both Fae activity (3.6 U/mg) and hexulose-6-phosphate synthase (Hps) activity (4.4 U/mg). The results support the recent proposal that in methanogenic archaea Fae and Hps could have a function in ribose phosphate synthesis.
Keywords: Methanogenic archaea; Methanosarcina mazei ; C1-metabolism; Ribulose monophosphate pathway; Methanogenesis from formaldehyde
Gene cloning and functional analysis of glycosaminoglycan-degrading enzyme chondroitin AC lyase from Flavobacterium columnare G4 by Hai X. Xie; P. Nie; M. X. Chang; Y. Liu; W. J. Yao (pp. 49-55).
The chondroitin AC lyase gene, cslA, was cloned for the first time from the fish bacterial pathogen F. columnare G4. From the first transcription initiation site, the cslA extends 2620 nucleotides to the end of the 3′ region. The open reading frame of cslA transcript has 2286 nucleotides encoding 762 amino acids with a 16 residues long signal peptide at the N-terminus. The gene, cslA was then successfully expressed in Escherichia coli and recombinant chondroitin AC lyase, rChonAC was purified, with its lytic activity analyzed. Zymography analysis copolymerized with chondroitin sulphate revealed the lytic activity of rChonAC and also the crude native ChonAC isolated from periplamic space of cultured F. columnare G4. The low level of lytic activity observed in crude native ChonAC may be due possibly to the low level of expression of this gene in the cultured condition. The expression and the role of this virulence factor is of interest for further research on the pathogenesis of F. columnare.
Keywords: Chondroitin AC lyase; Gene; Cloning; Recombinant protein; Lytic activity; Flavobacterium columnare G4
Gene cloning and functional analysis of glycosaminoglycan-degrading enzyme chondroitin AC lyase from Flavobacterium columnare G4 by Hai X. Xie; P. Nie; M. X. Chang; Y. Liu; W. J. Yao (pp. 49-55).
The chondroitin AC lyase gene, cslA, was cloned for the first time from the fish bacterial pathogen F. columnare G4. From the first transcription initiation site, the cslA extends 2620 nucleotides to the end of the 3′ region. The open reading frame of cslA transcript has 2286 nucleotides encoding 762 amino acids with a 16 residues long signal peptide at the N-terminus. The gene, cslA was then successfully expressed in Escherichia coli and recombinant chondroitin AC lyase, rChonAC was purified, with its lytic activity analyzed. Zymography analysis copolymerized with chondroitin sulphate revealed the lytic activity of rChonAC and also the crude native ChonAC isolated from periplamic space of cultured F. columnare G4. The low level of lytic activity observed in crude native ChonAC may be due possibly to the low level of expression of this gene in the cultured condition. The expression and the role of this virulence factor is of interest for further research on the pathogenesis of F. columnare.
Keywords: Chondroitin AC lyase; Gene; Cloning; Recombinant protein; Lytic activity; Flavobacterium columnare G4
Role of trehalose synthesis pathways in salt tolerance mechanism of Rhodobacter sphaeroides f. sp. denitrificans IL106 by Fumihiro Makihara; Minoru Tsuzuki; Kiichi Sato; Shinji Masuda; Kenji V. P. Nagashima; Mitsuru Abo; Akira Okubo (pp. 56-65).
The photosynthetic bacterium Rhodobacter sphaeroides (R. sphaeroides) f. sp. denitrificans IL106 accumulates trehalose as the major organic osmoprotectant in response to a salt stress. An analysis of the R. sphaeroides 2.4.1 genome sequence revealed the presence of five different genes encoding enzymes belonging to three putative trehalose biosynthesis pathways (OtsA-OtsB, TreY-TreZ, and TreS). The function of the different pathways of trehalose was studied by characterizing strains defective in individual trehalose biosynthetic routes. A phenotypic comparison revealed that trehalose synthesis in R. sphaeroides f. sp. denitrificans IL106 is mediated mainly by the OtsA-OtsB pathway and, to some extent, by the TreY-TreZ pathway. Strains with the simultaneous inactivation of these two pathways were completely unable to synthesize trehalose. On the other hand, treS mutants showed an increase in the trehalose level. These results suggest that treS plays a role in trehalose degradation. In addition, treS was found to be important in reducing trehalose after osmotic stress was removed. In this report, we show that the strains that accumulate the most trehalose adapt to salt stress earlier. This is the first report of an organism using multiple pathways to synthesize trehalose solely for use as a compatible solute against salt stress.
Keywords: Rhodobacter sphaeroides ; Trehalose; Salt stress
Role of trehalose synthesis pathways in salt tolerance mechanism of Rhodobacter sphaeroides f. sp. denitrificans IL106 by Fumihiro Makihara; Minoru Tsuzuki; Kiichi Sato; Shinji Masuda; Kenji V. P. Nagashima; Mitsuru Abo; Akira Okubo (pp. 56-65).
The photosynthetic bacterium Rhodobacter sphaeroides (R. sphaeroides) f. sp. denitrificans IL106 accumulates trehalose as the major organic osmoprotectant in response to a salt stress. An analysis of the R. sphaeroides 2.4.1 genome sequence revealed the presence of five different genes encoding enzymes belonging to three putative trehalose biosynthesis pathways (OtsA-OtsB, TreY-TreZ, and TreS). The function of the different pathways of trehalose was studied by characterizing strains defective in individual trehalose biosynthetic routes. A phenotypic comparison revealed that trehalose synthesis in R. sphaeroides f. sp. denitrificans IL106 is mediated mainly by the OtsA-OtsB pathway and, to some extent, by the TreY-TreZ pathway. Strains with the simultaneous inactivation of these two pathways were completely unable to synthesize trehalose. On the other hand, treS mutants showed an increase in the trehalose level. These results suggest that treS plays a role in trehalose degradation. In addition, treS was found to be important in reducing trehalose after osmotic stress was removed. In this report, we show that the strains that accumulate the most trehalose adapt to salt stress earlier. This is the first report of an organism using multiple pathways to synthesize trehalose solely for use as a compatible solute against salt stress.
Keywords: Rhodobacter sphaeroides ; Trehalose; Salt stress
Accumulation and turnover of 23S ribosomal RNA in azithromycin-inhibited ribonuclease mutant strains of Escherichia coli by Jessica A. Silvers; W. Scott Champney (pp. 66-77).
Ribosomal RNA is normally a stable molecule in bacterial cells with negligible turnover. Antibiotics which impair ribosomal subunit assembly promote the accumulation of subunit intermediates in cells which are then degraded by ribonucleases. It is predicted that cells expressing one or more mutated ribonucleases will degrade the antibiotic-bound particle less efficiently, resulting in increased sensitivity to the antibiotic. To test this, eight ribonuclease-deficient strains of Escherichia coli were grown in the presence or absence of azithromycin. Cell viability and protein synthesis rates were decreased in these strains compared with wild type cells. Degradation of 23S rRNA and recovery from azithromycin inhibition were examined by 3H-uridine labeling and by hybridization with a 23S rRNA specific probe. Mutants defective in ribonuclease II and polynucleotide phosphorylase demonstrated hypersensitivity to the antibiotic and showed a greater extent of 23S rRNA accumulation and a slower recovery rate. The results suggest that these two ribonucleases are important in 23S rRNA turnover in antibiotic-inhibited E. coli cells.
Keywords: Azithromycin; 50S ribosomal subunit; 23S rRNA; Ribonucleases; E. coli ; Ribosomes; Antibiotic inhibition
Accumulation and turnover of 23S ribosomal RNA in azithromycin-inhibited ribonuclease mutant strains of Escherichia coli by Jessica A. Silvers; W. Scott Champney (pp. 66-77).
Ribosomal RNA is normally a stable molecule in bacterial cells with negligible turnover. Antibiotics which impair ribosomal subunit assembly promote the accumulation of subunit intermediates in cells which are then degraded by ribonucleases. It is predicted that cells expressing one or more mutated ribonucleases will degrade the antibiotic-bound particle less efficiently, resulting in increased sensitivity to the antibiotic. To test this, eight ribonuclease-deficient strains of Escherichia coli were grown in the presence or absence of azithromycin. Cell viability and protein synthesis rates were decreased in these strains compared with wild type cells. Degradation of 23S rRNA and recovery from azithromycin inhibition were examined by 3H-uridine labeling and by hybridization with a 23S rRNA specific probe. Mutants defective in ribonuclease II and polynucleotide phosphorylase demonstrated hypersensitivity to the antibiotic and showed a greater extent of 23S rRNA accumulation and a slower recovery rate. The results suggest that these two ribonucleases are important in 23S rRNA turnover in antibiotic-inhibited E. coli cells.
Keywords: Azithromycin; 50S ribosomal subunit; 23S rRNA; Ribonucleases; E. coli ; Ribosomes; Antibiotic inhibition
Differential expression and extent of fungal/plant and fungal/bacterial chitinases of Aspergillus fumigatus by Mariam Taib; John W. Pinney; David R. Westhead; Kenneth J. McDowall; David J. Adams (pp. 78-81).
We provide the first indication of the extent of the complex chitinolytic system of a filamentous fungus. Phylogenetic analysis of the 14 apparent chitinases of the opportunistic fungal pathogen Aspergillus fumigatus identified four and ten enzymes related to plant and bacterial chitinases, respectively. Further, real time-RT-PCR studies revealed distinct patterns of gene expression, consistent with morphogenetic or nutritional roles, for members of the fungal/plant or fungal/bacterial sub-families, respectively. Our results provide a basis for future studies with A. fumigatus chitinases, which may lead to the exploitation of these enzymes, or their regulators, in the development of novel drug strategies.
Keywords: Chitinase sub-families; Aspergillus fumigatus ; Real time-RT-PCR; Transcriptional regulation
Differential expression and extent of fungal/plant and fungal/bacterial chitinases of Aspergillus fumigatus by Mariam Taib; John W. Pinney; David R. Westhead; Kenneth J. McDowall; David J. Adams (pp. 78-81).
We provide the first indication of the extent of the complex chitinolytic system of a filamentous fungus. Phylogenetic analysis of the 14 apparent chitinases of the opportunistic fungal pathogen Aspergillus fumigatus identified four and ten enzymes related to plant and bacterial chitinases, respectively. Further, real time-RT-PCR studies revealed distinct patterns of gene expression, consistent with morphogenetic or nutritional roles, for members of the fungal/plant or fungal/bacterial sub-families, respectively. Our results provide a basis for future studies with A. fumigatus chitinases, which may lead to the exploitation of these enzymes, or their regulators, in the development of novel drug strategies.
Keywords: Chitinase sub-families; Aspergillus fumigatus ; Real time-RT-PCR; Transcriptional regulation