Characterization of Actinobacillus seminis biofilm formation

Actinobacillus seminis DnaK interacts with bovine transferrin, lactoferrin, and hemoglobin as a putative iron acquisition mechanism

Ovine epididymitis, caused by Actinobacilus seminis, is an infectious disease that produces atrophy of the testis, low fertility, and sterility in infected animals. Iron is a microelement necessary for different vital functions in all organisms and most microorganisms. A. seminis iron acquisition mechanisms are undiscovered. For this reason, this work aimed to know the mechanisms this bacterium possesses to respond when grown in an iron restriction culture medium. A. seminis up-expressed three proteins, including a transferrin binding protein, and down-expressed seven (enzymes and putative adhesins) proteins when grown with 2,2'dipyridyl. With chelate, its growth was reduced by 40%, but it was recovered by adding 50-µM FeCl3. No siderophore production was detected with the CAS-BHI medium assay, but siderophore transporter proteins are present. Under normal growth conditions, this microorganism expresses a protein of 70 kDa, identified by mass spectrometry as DnaK. A. seminis DnaK interacts with biotin-labeled transferrin, lactoferrin, or bovine hemoglobin but not with biotin-labeled apo-transferrin or apo-lactoferrin, suggesting its participation in iron acquisition. This protein diminished its expression in iron restriction conditions at 37 °C but remained unchanged at 40 °C, and it is immune recognized by sheep serum with epididymitis. These different iron acquisition mechanisms could give rise to A. seminis, infecting different host tissues.

Epinephrine and norepinephrine regulate the expression of virulence factors in Gallibacterium anatis

Gallibacterium anatis is a member of the Pasteurellaceae family and is an opportunistic pathogen that causes gallibacteriosis in chickens. Stress plays a relevant role in promoting the development of pathogenicity in G. anatis. Epinephrine (E) and norepinephrine (NE) are relevant to stress; however, their effects on G. anatis have not been elucidated. In this work, we evaluated the effects of E and NE on the growth, biofilm formation, expression of adhesins, and proteases of two G. anatis strains, namely, the hemolytic 12656-12 and the nonhemolytic F149T biovars. E (10 μM/mL) and NE (30 and 50 μM/mL) increased the growth of G. anatis 12656-12 by 20 % and 25 %, respectively. E did not affect the growth of F149T, whereas 40 μM/mL NE decreased bacterial growth by 25 %. E and NE at a dose of 30-50 μM/mL upregulated five fibrinogen adhesins in the 12565-12 strain, whereas no effect was observed in the F149T strain. NE increased proteolytic activity in both strains, whereas E diminished proteolytic activity in the 12656-12 strain. E and NE reduced biofilm formation (30 %) and increased Congo red binding (15 %) in both strains. QseBC is the E and NE two-component detection system most common in bacteria. The qseC gene, which is the E and NE receptor in bacteria, was identified in the genomic DNA of the 12565-12 and F149TG. anatis strains via PCR amplification. Our results suggest that QseC can detect host changes in E and NE concentrations and that catecholamines can modulate the expression of several virulence factors in G. anatis.

Biochar combined with Bacillus subtilis SL-44 as an eco-friendly strategy to improve soil fertility, reduce Fusarium wilt, and promote radish growth

Bacillus subtilis as microbial fertilizers contribute to avoiding the harmful effects of traditional agricultural fertilizers and pesticides. However, there are many restrictions on the practical application of fertilizers. In this study, microbial biochar formulations (BCMs) were prepared by loading biochar with B. subtilis SL-44. Pot experiments were conducted to evaluate the effects of the BCMs on soil fertility, Fusarium wilt control, and radish plant growth. The application of BCMs dramatically improved soil properties and favored plant growth. Compared with SL-44 and biochar treatments, the BCMs treatments increased radish plant physical-chemical properties and activities of several enzymes in the soil. What's more, Fusarium wilt incidence had decreased by 59.88%. In addition, the BCMs treatments exhibited a significant increase in the abundance of bacterial genera in the rhizosphere soil of radish. Therefore, this study demonstrated that BCMs may be an eco-friendly strategy for improving soil fertility, reducing Fusarium wilt, and promoting radish plant growth.

Testosterone and estradiol modify the expression of adhesins and biofilm formation in Actinobacillus seminis

Actinobacillus seminis is the causal agent of epididymitis and has other effects on the reproductive tracts of small ruminants and bovines. This bacterium causes infection when luteinizing (LH) or follicle-stimulating hormones increase, and hosts reach sexual maturity. LH induces female ovulation and male testosterone production, suggesting that these hormones affect A. seminis pathogenicity. In the present study, we evaluated the effect of testosterone (1-5 ng/ml) or estradiol (5-25 pg/ml) added to culture medium on the in vitro growth, biofilm production, and adhesin expression of A. seminis. Estradiol does not promote the growth of this bacterium, whereas testosterone increased A. seminis planktonic growth 2-fold. Both hormones induced the expression of the elongation factor thermo unstable (EF-Tu) and phosphoglycerate mutase (PGM), proteins that A. seminis uses as adhesins. Estradiol (5 or 10 pg/ml) decreased biofilm formation by 32%, whereas testosterone, even at 5 ng/ml, showed no effect. Both hormones modified the concentrations of carbohydrates and eDNA in biofilms by 50%. Amyloid proteins are characterized by their capacity to bind Congo red (CR) dye. Actinobacillus seminis binds CR dye, and this binding increases in the presence of 5-20 pg/ml estradiol or 4 ng/ml testosterone. The A. seminis EF-Tu protein was identified as amyloid-like protein (ALP). The effect of sexual hormones on the growth and expression of virulence factors of A. seminis seems to be relevant for its colonization and permanence in the host.

Characterizing the vaginal microbiota of high and low producing Poll Merino and White Suffolk ewes

There is a substantial, and growing, body of research focused on manipulating gastrointestinal microbes to affect health and production. However, the maternal vaginal microbiota and its effects on neonatal inoculation and lifetime production have received little attention. We aimed to characterize the vaginal microbes of domesticated sheep to determine whether they differ across sheep breeds with differing meat and wool growth potentials and to determine a link between vaginal microbes and high and low producing animals. A flock of White Suffolk (n = 136) and Poll Merino (n = 210) ewes were sorted by the Australian Sheep Breeding Values (ASBV), for yearling fleece weight in the Merino and by post-weaning weight in the Suffolk ewes. The top and bottom ASBV sheep were selected for sampling and the resulting treatment groups were; High Suffolk (n = 12), Low Suffolk (n = 12), High Merino (n = 12), and Low Merino (n = 12) ewes. A double guarded culture swab was used to sample from the surface of the vaginal epithelium. Diversity profiling analysis of vaginal bacterial communities was conducted using 16S rRNA amplicon sequencing. Breed and ASBV group differences in bacterial communities were tested. Within breed, there were no significant differences in ewe vaginal bacterial communities associated with ewe production parameters; however, there was a significant difference in ewe vaginal bacterial communities between breeds. We have been able to characterize the normal vaginal microbiota of nonpregnant ewes and demonstrate a rich microbial community.

Mannheimia haemolytica OmpH binds fibrinogen and fibronectin and participates in biofilm formation

Mannheimia haemolytica is the causal agent of the shipping fever in bovines and produces high economic losses worldwide. This bacterium possesses different virulence attributes to achieve a successful infection. One of the main virulence factors expressed by a pathogen is through adhesion molecules; however, the components participating in this process are not totally known. The present work identified a M. haemolytica 41 kDa outer membrane protein (Omp) that participates in bacterial adhesion. This protein showed 100% identity with the OmpH from M. haemolytica as determined by mass spectrometry and it interacts with sheep fibrinogen. The 41 kDa M. haemolytica OmpH interacts with bovine monocytes; a previous incubation of M. haemolytica with a rabbit hyperimmune serum against this Omp diminished 45% cell adhesion. The OmpH was recognized by serum from bovines affected by acute or chronic pneumonia, indicating its in vivo expression; moreover, it showed immune cross-reaction with the serum of rabbit infected with Pasteurella multocida. The OmpH is present in biofilms and previous incubation of M. haemolytca with rabbit serum against this protein diminished biofilm, indicating this protein's participation in biofilm formation. M. haemolytica OmpH is proposed as a relevant immunogen in bovine pneumonia protection.