Analysis of high CO2 requiring mutants indicates a central role for the 5′ flanking region of rbc and for the carboxysomes in cyanobacterial photosynthesis

1990 ◽  
Vol 68 (6) ◽  
pp. 1303-1310 ◽  
Author(s):  
Aaron Kaplan
Keyword(s):  
Inorganic Carbon ◽  
Quantitative Model ◽  
Photosynthetic Performance ◽  
Kanamycin Resistance ◽  
Open Reading Frames ◽  
Bisphosphate Carboxylase ◽  
Insertional Inactivation ◽  
Flanking Region ◽  
Inorganic Carbon Transport ◽  
Reading Frames

The mutants E1 and O221, isolated from Synechococcus sp. PCC7942, exhibit a very low apparent photosynthetic affinity for both extracellular and intracellular inorganic carbon and hence require high CO2 concentrations for growth. These mutants possess defective carboxysomes, but the activity of ribulose 1,5-bisphosphate carboxylase is normal. The mutations in these mutants have been mapped to the 5′-flanking region of rbc, and two open reading frames, the functions of which are not yet known, have been identified in this region. Insertional inactivation (by inserting a kanamycin-resistance cartridge) of one of these open reading frames, where the mutation in O221 is located, resulted in a new high CO2 requiring phenotype. This mutant contains defective carboxysomes similar to those of O221. The role of the rbc and its 5′-flanking region in the photosynthetic performance of cyanobacteria and the structural organization of the carboxysomes are discussed in view of our recently proposed quantitative model for inorganic carbon transport and photosynthesis in cyanobacteria.

Physiological aspects of CO2 and HCO3− transport by cyanobacteria: a review

1990 ◽  
Vol 68 (6) ◽  
pp. 1291-1302 ◽  
Author(s):  
Anthony G. Miller ◽  
George S. Espie ◽  
David T. Canvin
Keyword(s):  
Active Transport ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Structural Analog ◽  
Transport Systems ◽  
Ribulose Bisphosphate Carboxylase ◽  
High Concentration ◽  
Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate Carboxylase Oxygenase ◽  
Inorganic Carbon Transport

Cyanobacteria grown at air levels of CO2, or lower, have a very high photosynthetic affinity for CO2. For ceils grown in carbon-limited chemostats at pH 9.6, the K0.5 (CO2) for whole cell CO2 fixation is about 3 nM. This is in spite of a K0.5 (CO2) for cyanobacterial ribulose bisphosphate carboxylase/oxygenase of about 200 μM. It is now clear that cyanobacteria can photosynthesize at very low CO2 concentrations because they raise the CO2 concentration dramatically around the carboxylase. This rise in the intracellular CO2 concentration involves the active transport of HCO3− and CO2, perhaps by separate transport systems. The transport of HCO3− often requires millimolar levels of Na+, and this provides a ready means of initiating HCO3− transport. The active transport of CO2 requires only micromolar levels of Na+. In the rather dense cell suspensions used in transport studies the extent of CO2 uptake is often limited by the rate at which CO2 can be formed from the HCO3− in the medium. The addition of carbonic anhydrase relieves this kinetic limitation on CO2 transport. The active transport of CO2 can be selectively inhibited by the structural analog carbon oxysulfide (COS). When HCO3− transport is allowed in the presence of COS there is a substantial net leakage of CO2 from the cells. This leaked CO2 results from the intracellular dehydration of the accumulated HCO3−. This CO2 is normally scavenged by the active CO2 pump. If cells are allowed to transport H13C18O18O18O− for 5 s and if CO2 transport is suddenly quenched by the addition of COS, then a rapid leakage of 13C16O16O occurs. If the rapidly released CO2 was actually present in the cells before the addition of the COS, then the intracellular CO2 concentration would have been about 0.6 mM. Not only is this a high concentration, but since the leaked CO2 was completely depleted of the initial 18O, it must have been in rapid equilibrium with the total dissolved inorganic carbon within the cells. Cells grown on high levels of inorganic carbon, either as CO2 or HCO3−, lack the active HCO3− system but still retain a capacity, albeit reduced, for CO2 transport. Cyanobacteria seem to adjust their complement of inorganic carbon transport systems so that the K0.5 for transport is close to the inorganic carbon concentration of the growth medium.

Environmental regulation of CO2-concentrating mechanisms in microalgae

1998 ◽  
Vol 76 (6) ◽  
pp. 1010-1017 ◽  
Author(s):  
John Beardall ◽  
Andrew Johnston ◽  
John Raven
Keyword(s):  
Inorganic Carbon ◽  
Light Availability ◽  
Phosphorus Limitation ◽  
Aeration Rate ◽  
Carbon Accumulation ◽  
Ribulose Bisphosphate Carboxylase ◽  
Carbon Utilization ◽  
Bisphosphate Carboxylase ◽  
Inorganic Carbon Transport ◽  
Carbon Transport

Most microalgae possess a mechanism for actively transporting inorganic carbon that concentrates CO2 at the active site of the carbon fixing enzyme ribulose bisphosphate carboxylase-oxygenase (Rubisco). This review considers the effects of environmental factors on the capacity and activity of microalgal CO2-concentrating mechanisms. Limitation of energy supply by light availability decreases the rate of inorganic carbon transport and cells grown under light-limited conditions have a reduced capacity for CO2 accumulation. Phosphorus limitation also reduces the capacity of algal cells to accumulate CO2, whereas both the rate of supply of nitrogen and the form in which it is made available interact in various complex ways with carbon utilization. The potential role of other nutrients in modulating inorganic carbon transport is also discussed. The capacity of algae for carbon accumulation is also affected by CO2 supply, which, in turn, is a function of the interactions between ionic strength of the growth medium, pH, cell density in culture, aeration rate, and inorganic carbon concentration in the medium. The effects of these interacting parameters are discussed, together with an assessment of the possible roles and significance of CO2-concentrating mechanisms to microalgae in marine and freshwater ecosystems.Key words: carbon acquisition, microalgae, CO2-concentrating mechanism, light, nutrient limitation, CO2 supply.

scholarly journals An O-Phosphotransferase Catalyzes Phosphorylation of Hygromycin A in the Antibiotic-Producing Organism Streptomyces hygroscopicus

2008 ◽  
Vol 52 (10) ◽  
pp. 3580-3588 ◽  
Author(s):  
Vidya Dhote ◽  
Shuchi Gupta ◽  
Kevin A. Reynolds
Keyword(s):  
Ribosomal Subunit ◽  
Biosynthetic Gene Cluster ◽  
Open Reading Frames ◽  
Streptomyces Hygroscopicus ◽  
Gram Negative Bacteria ◽  
E Coli ◽  
Naturally Occurring ◽  
Insertional Inactivation ◽  
Pathway Regulation ◽  
Reading Frames

ABSTRACT The antibiotic hygromycin A (HA) binds to the 50S ribosomal subunit and inhibits protein synthesis in gram-positive and gram-negative bacteria. The HA biosynthetic gene cluster in Streptomyces hygroscopicus NRRL 2388 contains 29 open reading frames, which have been assigned putative roles in biosynthesis, pathway regulation, and self-resistance. The hyg21 gene encodes an O-phosphotransferase with a proposed role in self-resistance. We observed that insertional inactivation of hyg21 in S. hygroscopicus leads to a greater than 90% decrease in HA production. The wild type and the hyg21 mutant were comparably resistant to HA. Using Escherichia coli as a heterologous host, we expressed and purified Hyg21. Kinetic analyses revealed that the recombinant protein catalyzes phosphorylation of HA (Km = 30 ± 4 μM) at the C-2‴ position of the fucofuranose ring in the presence of ATP (Km = 200 ± 20 μM) or GTP (Km = 350 ± 60 μM) with a k cat of 2.2 ± 0.1 min−1. The phosphorylated HA is inactive against HA-sensitive ΔtolC E. coli and Streptomyces lividans. Hyg21 also phosphorylates methoxyhygromycin A and desmethylenehygromycin A with k cat and Km values similar to those observed with HA. Phosphorylation of the naturally occurring isomers of 5‴-dihydrohygromycin A and 5‴-dihydromethoxyhygromycin A was about 12 times slower than for the corresponding non-natural isomers. These studies demonstrate that Hyg21 is an O-phosphotransferase with broad substrate specificity, tolerating changes in the aminocyclitol moiety more than in the fucofuranose moiety, and that phosphorylation by Hyg21 is one of several possible mechanisms of self-resistance in S. hygroscopicus NRRL 2388.

scholarly journals Synthesis of Catalytically Active Form III Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase in Archaea

2003 ◽  
Vol 185 (10) ◽  
pp. 3049-3059 ◽  
Author(s):  
Michael W. Finn ◽  
F. Robert Tabita
Keyword(s):  
Rhodobacter Capsulatus ◽  
Quaternary Structure ◽  
Active Form ◽  
Normal Growth ◽  
Growth Conditions ◽  
Methanosarcina Barkeri ◽  
Open Reading Frames ◽  
Bisphosphate Carboxylase ◽  
Biological Reduction ◽  
Reading Frames

ABSTRACT Ribulose 1,5 bisphosphate carboxylase/oxygenase (RubisCO) catalyzes the biological reduction and assimilation of carbon dioxide gas to organic carbon; it is the key enzyme responsible for the bulk of organic matter found on earth. Until recently it was believed that there are only two forms of RubisCO, form I and form II. However, the recent completion of several genome-sequencing projects uncovered open reading frames resembling RubisCO in the third domain of life, the archaea. Previous work and homology comparisons suggest that these enzymes represent a third form of RubisCO, form III. While earlier work indicated that two structurally distinct recombinant archaeal RubisCO proteins catalyzed bona fide RubisCO reactions, it was not established that the rbcL genes of anaerobic archaea can be transcribed and translated to an active enzyme in the native organisms. In this report, it is shown not only that Methanococcus jannaschii, Archaeoglobus fulgidus, Methanosarcina acetivorans, and Methanosarcina barkeri possess open reading frames with the residues required for catalysis but also that the RubisCO protein from these archaea accumulates in an active form under normal growth conditions. In addition, the form III RubisCO gene (rbcL) from M. acetivorans was shown to complement RubisCO deletion strains of Rhodobacter capsulatus and Rhodobacter sphaeroides under both photoheterotrophic and photoautotrophic growth conditions. These studies thus indicate for the first time that archaeal form III RubisCO functions in a physiologically significant fashion to fix CO2. Furthermore, recombinant M. jannaschii, M. acetivorans, and A. fulgidus RubisCO possess unique properties with respect to quaternary structure, temperature optima, and activity in the presence of molecular oxygen compared to the previously described Thermococcus kodakaraensis and halophile proteins.

scholarly journals Identification of the Novobiocin Biosynthetic Gene Cluster of Streptomyces spheroides NCIB 11891

2000 ◽  
Vol 44 (5) ◽  
pp. 1214-1222 ◽  
Author(s):  
Marion Steffensky ◽  
Agnes Mühlenweg ◽  
Zhao-Xin Wang ◽  
Shu-Ming Li ◽  
Lutz Heide
Keyword(s):  
Heterologous Expression ◽  
Gene Cluster ◽  
Biosynthetic Gene Cluster ◽  
Streptomyces Lividans ◽  
Open Reading Frames ◽  
Biosynthetic Gene ◽  
Insertional Inactivation ◽  
Key Enzyme ◽  
Novobiocin Resistance ◽  
Reading Frames

ABSTRACT The novobiocin biosynthetic gene cluster from Streptomyces spheroides NCIB 11891 was cloned by using homologous deoxynucleoside diphosphate (dNDP)-glucose 4,6-dehydratase gene fragments as probes. Double-stranded sequencing of 25.6 kb revealed the presence of 23 putative open reading frames (ORFs), including the gene for novobiocin resistance, gyrB r, and at least 11 further ORFs to which a possible role in novobiocin biosynthesis could be assigned. An insertional inactivation experiment with a dNDP-glucose 4,6-dehydratase fragment resulted in abolishment of novobiocin production, since biosynthesis of the deoxysugar moiety of novobiocin was blocked. Heterologous expression of a key enzyme of novobiocin biosynthesis, i.e., novobiocic acid synthetase, inStreptomyces lividans TK24 further confirmed the involvement of the analyzed genes in the biosynthesis of the antibiotic.

A model for inorganic carbon fluxes and photosynthesis in cyanobacterial carboxysomes

1991 ◽  
Vol 69 (5) ◽  
pp. 984-988 ◽  
Author(s):  
Leonora Reinhold ◽  
Ronnie Kosloff ◽  
Aaron Kaplan
Keyword(s):  
Inorganic Carbon ◽  
Three Dimensional ◽  
Diffusion Path ◽  
Carbon Fluxes ◽  
Quantitative Model ◽  
Key Words Cyanobacteria ◽  
Bisphosphate Carboxylase ◽  
Permeability Constant ◽  
A Value ◽  
Dimensional Diffusion

A barrier to CO2 diffusion within the cyanobacterial cell has been regarded as essential for the inorganic carbon concentrating mechanism. We present here an extension of our earlier quantitative model demonstrating that it may be unnecessary to postulate any barrier other than the ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) molecules themselves. It is proposed that carbonic anhydrase is located in the interior of the carboxysome and that the CO2 generated is largely fixed as it diffuses outwards past Rubisco sites located along the diffusion path. Equations have been developed, by combining a mass balance equation with Fick's Law and the Michaelis-Menten equation (representing CO2 fixation), estimate the value that must be assigned to the diffusion coefficient for CO2 within the carboxysome if the CO2 concentration is to be reduced to near zero at the carboxysome outer surface. A solution has been obtained for two limiting cases, that where CO2 concentration is nearly saturating and that where it is at the Km(CO2) value or below. These two estimates predict that the permeability constant for the Rubisco zone in the carboxysome would have to be 10−2–10−3 cm∙s−1, a value that we suggest is reasonable for three-dimensional diffusion through a densely packed protein layer. The concentration gradient in the inward direction, for substrates penetrating the carboxysomes from the cytoplasm, is shown to be relatively flat, owing to the concentrating effect experienced by solutes passing from the periphery to the center of a sphere. Key words: cyanobacteria, carboxysomes, inorganic carbon fluxes, photosynthesis, model.

scholarly journals Assembly of the K40 Antigen in Escherichia coli: Identification of a Novel Enzyme Responsible for Addition ofl-Serine Residues to the Glycan Backbone and Its Requirement for K40 Polymerization

1999 ◽  
Vol 181 (3) ◽  
pp. 772-780 ◽  
Author(s):  
Paul A. Amor ◽  
Jeremy A. Yethon ◽  
Mario A. Monteiro ◽  
Chris Whitfield
Keyword(s):  
Escherichia Coli ◽  
Lipid A ◽  
Glucuronic Acid ◽  
Repeat Unit ◽  
Compositional Analysis ◽  
Open Reading Frames ◽  
Insertional Inactivation ◽  
Dependent Pathway ◽  
Reading Frames ◽  
Polyclonal Serum

ABSTRACT Escherichia coli O8:K40 coexpresses two distinct lipopolysaccharide (LPS) structures on its surface. The O8 polysaccharide is a mannose homopolymer with a trisaccharide repeat unit and is synthesized by an ABC-2 transport-dependent pathway. The K40LPS backbone structure is composed of a trisaccharide repeating unit of N-acetylglucosamine (GlcNAc) and glucuronic acid (GlcA) and has an uncommon substitution, anl-serine moiety attached to glucuronic acid. The gene cluster responsible for synthesis of the K40 polysaccharide has previously been cloned and sequenced and was found to contain six open reading frames (ORFs) (P. A. Amor and C. Whitfield, Mol. Microbiol. 26:145–161, 1997). Here, we demonstrate that insertional inactivation of orf1 results in the accumulation of a semirough (SR)-K40LPS form which retains reactivity with specific polyclonal serum in Western immunoblots. Structural and compositional analysis of the SR-K40LPS reveals that it comprises a single K40 repeat unit attached to lipid A core. The lack of polymerization of the K40 polysaccharide indicates thatorf1 encodes the K40 polymerase (Wzy) and that assembly of the K40 polysaccharide occurs via a Wzy-dependent pathway (in contrast to that of the O8 polysaccharide). Inactivation of orf3also results in the accumulation of an SR-LPS form which fails to react with specific polyclonal K40 serum in Western immunoblots. Methylation linkage analysis and fast atom bombardment-mass spectrometry of this SR-LPS reveals that the biological repeat unit of the K40 polysaccharide is GlcNAc-GlcA-GlcNAc. Additionally, this structure lacks the l-serine substitution of GlcA. These results show that (i) orf3 encodes the enzyme responsible for the addition of the l-serine residue to the K40 backbone and (ii) substitution of individual K40 repeats withl-serine is essential for their recognition and polymerization into the K40 polysaccharide by Wzy.

Cloning and characterization of the genes required for inorganic carbon transport of Synechocystis PCC6803

1991 ◽  
Vol 69 (5) ◽  
pp. 951-956 ◽  
Author(s):  
Teruo Ogawa
Keyword(s):  
Nadh Dehydrogenase ◽  
Inorganic Carbon ◽  
Wild Type ◽  
Reading Frame ◽  
Synechocystis Pcc6803 ◽  
Dna Libraries ◽  
Insertional Inactivation ◽  
Inorganic Carbon Transport ◽  
Carbon Transport

Transformation of the high CO2-requiring mutants of Synechocystis PCC6803 defective in inorganic carbon (Ci) transport (RKa and RKb) by wild type (WT) DNA libraries restored their ability to grow under air levels of CO2. Two clones (PK-1 and HP-1), which complement RKa and RKb, respectively, were isolated from the libraries. PK-1 contained an 11.8-kilobase pair (kbp) DNA insert. The sequence of amino acid coded in the DNA in the region of the mutation showed an extensive homology to that of the ndh2 gene product of liverwort chloroplasts, which is suspected to be the subunit 2 of NADH dehydrogenase. Based on the result, we designated the gene mutated in RKa as ndh2. Inactivation of the ndh2 gene in the WT cells by inserting an aminoglycoside-3′-phosphotransferase gene generated a mutant (M57) that was unable to grow under low CO2 conditions. HP-1 contained a 5.4-kbp DNA insert. Sequencing of nucleotides in the region of the mutation revealed an open reading frame that codes a hydrophobic protein that consists of 80 amino acids. Insertional inactivation of this putative Ci transport gene, designated ictA, generated a high CO2-requiring mutant (M9). All these mutants (RKa, RKb, M9, and M57) showed very low activity of CO2 uptake into the intracellular Ci pools. The activity of HCO3− uptake was negligibly low in RKb, M9, M57 and high CO2-grown cells of RKa, and was about 10% the activity of wild type cells in low CO2-adapted cells of RKa. Key words: CO2-concentrating mechanism, inorganic carbon transport, Synechocystis PCC6803, mutant, NADH dehydrogenase, insertional inactivation.

scholarly journals A Novel Integrative Conjugative Element Mediates Genetic Transfer from Group G Streptococcus to Other β-Hemolytic Streptococci

2009 ◽  
Vol 191 (7) ◽  
pp. 2257-2265 ◽  
Author(s):  
Mark R. Davies ◽  
Josephine Shera ◽  
Gary H. Van Domselaar ◽  
Kadaba S. Sriprakash ◽  
David J. McMillan
Keyword(s):  
Group A Streptococcus ◽  
Bacterial Species ◽  
Group B Streptococcus ◽  
Gene Clusters ◽  
Kanamycin Resistance ◽  
Open Reading Frames ◽  
Cadmium Resistance ◽  
Integrative Conjugative Element ◽  
Group B ◽  
Reading Frames

ABSTRACT Lateral gene transfer is a significant contributor to the ongoing evolution of many bacterial pathogens, including β-hemolytic streptococci. Here we provide the first characterization of a novel integrative conjugative element (ICE), ICESde3396, from Streptococcus dysgalactiae subsp. equisimilis (group G streptococcus [GGS]), a bacterium commonly found in the throat and skin of humans. ICESde3396 is 64 kb in size and encodes 66 putative open reading frames. ICESde3396 shares 38 open reading frames with a putative ICE from Streptococcus agalactiae (group B streptococcus [GBS]), ICESa2603. In addition to genes involves in conjugal processes, ICESde3396 also carries genes predicted to be involved in virulence and resistance to various metals. A major feature of ICESde3396 differentiating it from ICESa2603 is the presence of an 18-kb internal recombinogenic region containing four unique gene clusters, which appear to have been acquired from streptococcal and nonstreptococcal bacterial species. The four clusters include two cadmium resistance operons, an arsenic resistance operon, and genes with orthologues in a group A streptococcus (GAS) prophage. Streptococci that naturally harbor ICESde3396 have increased resistance to cadmium and arsenate, indicating the functionality of genes present in the 18-kb recombinogenic region. By marking ICESde3396 with a kanamycin resistance gene, we demonstrate that the ICE is transferable to other GGS isolates as well as GBS and GAS. To investigate the presence of the ICE in clinical streptococcal isolates, we screened 69 isolates (30 GGS, 19 GBS, and 20 GAS isolates) for the presence of three separate regions of ICESde3396. Eleven isolates possessed all three regions, suggesting they harbored ICESde3396-like elements. Another four isolates possessed ICESa2603-like elements. We propose that ICESde3396 is a mobile genetic element that is capable of acquiring DNA from multiple bacterial sources and is a vehicle for dissemination of this DNA through the wider β-hemolytic streptococcal population.

scholarly journals Cloning and Mutagenesis of a Serotype-Specific DNA Region Involved in Encapsulation and Virulence of Actinobacillus pleuropneumoniae Serotype 5a: Concomitant Expression of Serotype 5a and 1 Capsular Polysaccharides in Recombinant A. pleuropneumoniae Serotype 1

1998 ◽  
Vol 66 (7) ◽  
pp. 3326-3336 ◽  
Author(s):  
Christine K. Ward ◽  
Mark L. Lawrence ◽  
Hugo P. Veit ◽  
Thomas J. Inzana
Keyword(s):  
Capsular Polysaccharide ◽  
Lethal Dose ◽  
Calf Serum ◽  
Actinobacillus Pleuropneumoniae ◽  
Kanamycin Resistance ◽  
Open Reading Frames ◽  
Kanamycin Resistance Cassette ◽  
Serotype 1 ◽  
Serotype 5 ◽  
Reading Frames

ABSTRACT A DNA region involved in Actinobacillus pleuropneumoniae serotype 5 capsular polysaccharide (CP) biosynthesis was identified and characterized by using a probe specific for the cpxD gene involved in CP export. The adjacent serotype 5-specific CP biosynthesis region was cloned from a 5.8-kbBamHI fragment and an 8.0-kb EcoRI fragment of strain J45 genomic DNA. DNA sequence analysis demonstrated that this region contained four complete open reading frames,cps5A, cps5B, cps5C, andcps5D. Cps5A, Cps5B, and Cps5C showed low homology with several bacterial glycosyltransferases involved in the biosynthesis of lipopolysaccharide or CP. However, Cps5D had high homology with KdsA proteins (3-deoxy-d-manno-2-octulosonic acid 8-phosphate synthetase) from other gram-negative bacteria. The G+C content of cps5ABC was substantially lower (28%) than that of cps5D and the rest of the A. pleuropneumoniae chromosome (42%). A 2.1-kb deletion spanning the cloned cps5ABC open reading frames was constructed and transferred into the J45 chromosome by homologous recombination with a kanamycin resistance cassette to produce mutant J45-100. Multiplex PCR confirmed the deletion in this region of J45-100 DNA. J45-100 did not produce intracellular or extracellular CP, indicating thatcps5A, cps5B, and/or cps5C were involved in CP biosynthesis. However, biosynthesis of the Apx toxins, lipopolysaccharide, and membrane proteins was unaffected by the mutation. Besides lack of CP biosynthesis, and in contrast to J45, J45-100 grew faster, was sensitive to killing in precolostral calf serum, and was avirulent in pigs at an intratracheal challenge dose three times the 50% lethal dose (LD50) of strain J45. At six times the J45 LD50, J45-100 caused mild to moderate lung lesions but not death. Electroporation of cps5ABC intoA. pleuropneumoniae serotype 1 strain 4074 generated strain 4074(pJMLCPS5), which expressed both serotype 1 and serotype 5 CP. However, serotype 1 capsule expression was diminished in 4074(pJMLCPS5) in comparison to 4074. The recombinant strain produced significantly less total CP (serotypes 1 and 5 CP combined) in log phase (P = 0.0012) but significantly more total CP in late stationary phase than 4074 (P < 0.0001). In addition, strain 4074(pJMLCPS5) caused less mortality and bacteremia in pigs and mice following respiratory challenge than strain 4074, indicating that virulence was affected by diminished capsule production. These results emphasize the importance of CP in the serum resistance and virulence of A. pleuropneumoniae.

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