Abstract: Mutants of P. haemolytica provide excellent safety and efficacy when used as vaccines in ruminants, for example cattle, sheep, and goats, subject to pneumonic pasteurellosis. They can be administered by a variety of routes. Especially preferred is the use in animal feeds. The mutants are not reverting and contain no foreign DNA and no introduced antibiotic resistance genes.

Abstract: Mutants of P. haemolytica provide excellent safety and efficacy when used as vaccines in ruminants, for example cattle, sheep, and goats, subject to pneumonic pasteurellosis. They can be administered by a variety of routes. Especially preferred is the use in animal feeds. The mutants are not reverting and contain no foreign DNA and no introduced antibiotic resistance genes.

Abstract: Mutants of P. haemolytica provide excellent safety and efficacy when used as vaccines in ruminants, for example cattle, sheep, and goats, subject to pneumonic pasteurellosis. They can be administered by a variety of routes. Especially preferred is the use in animal feeds. The mutants are not reverting and contain no foreign DNA and no introduced antibiotic resistance genes.

Abstract: Mutants of P. haemolytica provide excellent safety and efficacy when used as vaccines in ruminants, for example cattle, sheep, and goats, subject to pneumonic pasteurellosis. They can be administered by a variety of routes. Especially preferred is the use in animal feeds. The mutants are not reverting and contain no foreign DNA and no introduced antibiotic resistance genes.

Abstract: Mutants of P. haemolytica provide excellent safety and efficacy when used as vaccines in ruminants, for example cattle, sheep, and goats, subject to pneumonic pasteurellosis. They can be administered by a variety of routes. Especially preferred is the use in animal feeds. The mutants are not reverting and contain no foreign DNA and no introduced antibiotic resistance genes.

Abstract: Mutants of P. haemolytica provide excellent safety and efficacy when used as vaccines in ruminants, for example cattle, sheep, and goats, subject to pneumonic pasteurellosis. They can be administered by a variety of routes. Especially preferred is the use in animal feeds. The mutants are not reverting and contain no foreign DNA and no introduced antibiotic resistance genes.

Abstract: Virulence factor mutants of Pasteurellaceae provide excellent safety and efficacy when used as vaccines in mammals, especially ruminants, for example cattle, sheep, and goats, subject to pneumonic pasteurellosis. They can be administered by a variety of routes. Especially preferred is the use in animal feeds. The mutants are not reverting and contain no foreign DNA and no introduced antibiotic resistance genes.

Abstract: Methylation of DNA can be a critical step in the introduction of DNA into P. haemolytica. A methyltransferase has been isolated and molecularly cloned for this purpose. Use of the methyltransferase has allowed construction of defined, attenuated mutants for use as vaccines to protect cattle.

Abstract: Tools for genetically engineering Pasteurellaceae are provided. Replication-conditional plasmids which are useful for the Pasteurellaceae have been isolated and characterized. The plasmids can be utilized for delivery of DNA segments into the Pasteurellaceae in situations where control of extrachromosomal replication desired, such as in achieving allelic exchange or site-directed mutagenesis.A restriction endonuclease, HsoI, was isolated from a bovine lung isolate of Haemophilus somnus. The enzyme was found to be a true isoschizomer of HinPI, a commercially available enzyme originally isolated from Haemophilus influenzae PI. Commercially available HhaI methyl transferase was found to protect against cleavage by both enzymes. Methylation of foreign plasmid DNA was found to enhance transformation of Haemophilus somnus in excess of four orders of magnitude.

Abstract: Methylation of DNA can be a critical step in the introduction of DNA into P. haemolytica. A methyltransferase has been isolated and molecularly cloned for this purpose. Use of the methyltransferase has allowed construction of defined, attenuated mutants for use as vaccines to protect cattle.

Abstract: Methylation of DNA can be a critical step in the introduction of DNA into P. haemolytica. A methyltransferase has been isolated and molecularly cloned for this purpose. Use of the methyltransferase has allowed construction of defined, attenuated mutants for use as vaccines to protect cattle.

Abstract: Methylation of DNA can be a critical step in the introduction of DNA into P. haemolytica. A methyltransferase has been isolated and molecularly cloned for this purpose. Use of the methyltransferase has allowed construction of defined, attenuated mutants for use as vaccines to protect cattle.

Abstract: Methylation of DNA can be a critical step in the introduction of DNA into P. haemolytica. A methyltransferase has been isolated and molecularly cloned for this purpose. Use of the methyltransferase has allowed construction of defined, attenuated mutants for use as vaccines to protect cattle.

Abstract: Methylation of DNA can be a critical step in the introduction of DNA into P. haemolytica. A methyltransferase has been isolated and molecularly cloned for this purpose. Use of the methyltransferase has allowed construction of defined, attenuated mutants for use as vaccines to protect cattle.

Abstract: Tools for genetically engineering Pasteurellaceae are provided. Replication-conditional plasmids which are useful for the Pasteurellaceae have been isolated and characterized. The plasmids can be utilized for delivery of DNA segments into the Pasteurellaceae in situations where control of extra-chromosomal replication desired, such as in achieving allelic exchange or site-directed mutagenesis. A restriction endonuclease, HsoI, was isolated from a bovine lung isolate of Haemophilus somnus. The enzyme was found to be a true isoschizomer of HinPI, a commercially available enzyme originally isolated from Haemophilus influenzae PI. Commercially available HhaI methyl transferase was found to protect against cleavage by both enzymes. Methylation of foreign plasmid DNA was found to enhance transformation of Haemophilus somnus in excess of four orders of magnitude.