RESUMO
Mannheimia haemolytica causes respiratory disease in cattle. Amyloid proteins are a major component of biofilms; they aid in adhesion and confer resistance against several environmental insults. The amyloid protein curli is highly resistant to protease digestion and physical and chemical denaturation and binds Congo red (CR) dye. The purpose of this study was to characterize an approximately 50-kDa CR-binding amyloid-like protein (ALP) expressed by M. haemolytica. This protein resisted boiling and formic acid digestion and was recognized by a polyclonal anti-Escherichia coli curli serum, suggesting its relationship with amyloid proteins. Immunolabeling and transmission electron microscopy showed that antibodies bound long, thin fibers attached to the bacterial surface. Mass spectrometry analysis indicated that these fibers are M. haemolytica OmpP2-like proteins. The purified protein formed filaments in vitro, and antiserum against it reacted positively with biofilms. An in silico analysis of its amino acid sequence indicated it has auto-aggregation properties and eight amyloid peptides. Rabbit polyclonal antibodies generated against this ALP diminished the adhesion of ATCC 31612 and BA1 M. haemolytica strains to A549 human epithelial cells, indicating its participation in cell adhesion. ALP expressed by M. haemolytica may be important in its pathogenicity and ability to form biofilms.
Assuntos
Proteínas Amiloidogênicas/química , Proteínas da Membrana Bacteriana Externa/química , Biofilmes/crescimento & desenvolvimento , Mannheimia haemolytica/química , Células A549 , Sequência de Aminoácidos , Proteínas Amiloidogênicas/biossíntese , Proteínas Amiloidogênicas/genética , Proteínas Amiloidogênicas/isolamento & purificação , Animais , Aderência Bacteriana , Proteínas da Membrana Bacteriana Externa/biossíntese , Proteínas da Membrana Bacteriana Externa/genética , Proteínas da Membrana Bacteriana Externa/isolamento & purificação , Bovinos , Vermelho Congo/química , Expressão Gênica , Humanos , Soros Imunes/química , Soros Imunes/isolamento & purificação , Mannheimia haemolytica/genética , Mannheimia haemolytica/isolamento & purificação , Mannheimia haemolytica/metabolismo , Modelos Moleculares , Peso Molecular , Pasteurelose Pneumônica , Ligação Proteica , Estrutura Secundária de Proteína , Coelhos , Alinhamento de Sequência , OvinosRESUMO
Mannheimia haemolytica leukotoxin (LKT) is a known cause of bovine respiratory disease (BRD) which results in severe economic losses in the cattle industry (up to USD 1 billion per year in the USA). Vaccines based on LKT offer the most promising measure to contain BRD outbreaks and are already commercially available. However, insufficient LKT yields, predominantly reflecting a lack of knowledge about the LKT expression process, remain a significant engineering problem and further bioprocess optimization is required to increase process efficiency. Most previous investigations have focused on LKT activity and cell growth, but neither of these parameters defines reliable criteria for the improvement of LKT yields. In this article, we review the most important process conditions and operational parameters (temperature, pH, substrate concentration, dissolved oxygen level, medium composition and the presence of metabolites) from a bioprocess engineering perspective, in order to maximize LKT yields.
Assuntos
Animais , Bovinos , Toxinas Bacterianas/biossíntese , Mannheimia haemolytica/metabolismo , Complexo Respiratório Bovino/microbiologia , Exotoxinas/biossíntese , Temperatura , Oligoelementos , Carbono/metabolismo , Mannheimia haemolytica/patogenicidade , Aminoácidos/metabolismo , Concentração de Íons de Hidrogênio , CinetinaRESUMO
Mannheimia haemolytica is a Gram negative bacterium that is part of the bovine respiratory disease, which causes important economic losses in the livestock industry. In the present work, the interaction between M. haemolytica A1 and bovine lactoferrin (BLf) was studied. This iron-chelating glycoprotein is part of the mammalian innate-immune system and is present in milk and mucosal secretions; Lf is also contained in neutrophils secondary granules, which release this glycoprotein at infection sites. It was evidenced that M. haemolytica was not able to use iron-charged BLf (BholoLf) as a sole iron source; nevertheless, iron-lacked BLf (BapoLf) showed a bactericidal effect against M. haemolytica with MIC of 4.88 ± 1.88 and 7.31 ± 1.62 µM for M. haemolytica strain F (field isolate) and M. haemolytica strain R (reference strain), respectively. Through overlay assays and 2-D electrophoresis, two OMP of 32.9 and 34.2 kDa with estimated IP of 8.18 and 9.35, respectively, were observed to bind both BapoLf and BholoLf; these OMP were identified by Maldi-Tof as OmpA (heat-modifiable OMP) and a membrane protein (porin). These M. haemolytica BLf binding proteins could be interacting in vivo with both forms of BLf depending on the iron state of the bovine.