Medium optimization and dust suppression performance analysis of microbial-based dust suppressant compound by response surface curve method

At present, microbial dust suppressants based on microbial communities lack necessary systematic analysis of factors affecting dust suppression performance. Therefore, in this study, the response surface curve method was used to optimize the culture conditions for enrichment of urease-producing microorganisms from activated sludge. The results indicated that when urea = 9.67 g L-1, NH4Cl = 5.21 g L-1, and pH = 9.57, the maximum urease activity of urease-producing microbial community (UPMC) was 8.22 mM min-1. The UPMC under optimized culture conditions reached a mineralization rate of 98.8% on the 1st day of mineralization. Ureolysis is one of the biological mechanisms that trigger microbial mineralization with the consequent effect of dust suppression. The analysis of microbial community structure indicated that the urease-producing bacteria Sporosarcina sp. had the highest abundance at the genus level in the microbial-based dust suppressant compound. Jeotgalicoccus sp. plays an important role in improving and maintaining the stability of urease. In addition, the optimal UPMC had low pathogenicity, which is extremely attractive for the safe application of microbial dust suppressants.

Evaluating cpn60 for high-resolution profiling of the mammalian skin microbiome and detection of phylosymbiosis

Despite being the most widely used phylogenetic marker for amplicon-based profiling of microbial communities, limited phylogenetic resolution of the 16S rRNA gene limits its use for studies of host-microbe co-evolution. In contrast, the cpn60 gene is a universal phylogenetic marker with greater sequence variation capable of species-level resolution. This research compared mammalian skin microbial profiles generated from cpn60 and 16S rRNA gene sequencing approaches, testing for patterns of phylosymbiosis that suggest co-evolutionary host-microbe associations. An ~560 bp fragment of the cpn60 gene was amplified with universal primers and subjected to high-throughput sequencing. Taxonomic classification of cpn60 sequences was completed using a naïve-Bayesian QIIME2 classifier created for this project, trained with an NCBI-supplemented curated cpn60 database (cpnDB_nr). The cpn60 dataset was then compared to published 16S rRNA gene amplicon data. Beta diversity comparisons of microbial community profiles generated with cpn60 and 16S rRNA gene amplicons were not significantly different, based on Procrustes analysis of Bray-Curtis and UniFrac distances. Despite similar relationships among skin microbial profiles, improved phylogenetic resolution provided by the cpn60 gene sequencing permitted observations of phylosymbiosis between microbial community profiles and their mammalian hosts that were not previously observed with 16S rRNA gene profiles. Subsequent investigation of Staphylococcaceae taxa using the cpn60 gene showed increased phylogenetic resolution compared the 16S rRNA gene profiles, revealing potential co-evolutionary host-microbe associations. Overall, our results demonstrate that 16S rRNA and cpn60 marker genes generate comparable microbial community composition patterns while cpn60 better facilitates analyses, such as phylosymbiosis, that require increased phylogenetic resolution.

Jeotgalicoccus meleagridis sp. nov. isolated from bioaerosol from emissions of a turkey fattening plant and reclassification of Jeotgalicoccus halophilus Liu et al. 2011 as a later heterotypic synonym of Jeotgalicoccus aerolatus Martin et al. 2011

A Gram-stain-positive, non-motile, non-spore-forming, coccus (strain Do 184^T) was isolated from exhaust air of a turkey fattening plant on mannitol salt agar. The strain shared high 16S rRNA gene sequence similarity to the type strains of Jeotgalicoccus aerolatus (98.0%) followed by Jeotgalicoccus marinus (97.2%) and Jeotgalicoccus huakuii (97.1%). All other 16S rRNA gene sequence similarities to species of the genus Jeotgalicoccus were below 97%. The average nucleotide identities (ANI) between the Do 184^T genome assembly and the ones of type strains of species of the genus Jeotgalicoccus were far below the 95% species delineation cutoff value, ranging from 79.47% (J. marinus DSM 19772^T) to 75.30% (J. pinnipedialis CIP 107946^T). The quinone system of Do 184^T, the polar lipid profile, the polyamine pattern and the fatty acid profile were in congruence with those reported for other species of the genus Jeotgalicoccus and thus supported the affiliation of Do 184^T to this genus. Do 184^T represents a novel species, for which the name Jeotgalicoccus meleagridis sp. nov. is proposed, with the type strain Do 184^T (=LMG 31100^T=CCM 8918^T=CIP 111649^T). In addition, data on genome sequences of Jeotgalicoccus halophilus C1-52^T =CGMCC 1.8911^T=NBRC 105788^T and Jeotgalicoccus aerolatus MPA-33^T=CCM 7679^T=CCUG 57953^T=DSM 22420^T=CIP 111750^T indicate that both isolates represent the same species. Pairwise ANI between the genomes of these two strains lead to similarities of 98.98-99.05 %. These results indicate that these strains represent members of the same species. Due to priority of publication it is proposed that Jeotgalicoccus halophilus is reclassified as Jeotgalicoccus aerolatus.

Biochemical characterization of three new α-olefin-producing P450 fatty acid decarboxylases with a halophilic property

BACKGROUND

The CYP152 family member OleT_JE from Jeotgalicoccus sp. ATCC 8456 has been well-known to catalyze the unusual one-step decarboxylation of free fatty acids towards the formation of terminal alkenes. Efforts to tune up its decarboxylation activity for better production of biological alkenes have been extensively explored via approaches such as site-directed mutagenesis and electron source engineering, but with limited success. To gain more insights into the decarboxylation mechanism and reaction bifurcation (decarboxylation versus hydroxylation), we turned to an alternative approach to explore the natural CYP152 resources for a better variety of enzyme candidates.

RESULTS

We biochemically characterized three new P450 fatty acid decarboxylases including OleT_JH, OleT_SQ and OleT_SA, with respect to their substrate specificity, steady-state kinetics, and salt effects. These enzymes all act as an OleT_JE-like fatty acid decarboxylase being able to decarboxylate a range of straight-chain saturated fatty acids (C₈-C₂₀) to various degrees. Site-directed mutagenesis analysis to the lower activity P450 enzyme OleT_SA revealed a number of key amino acid residues within the substrate-binding pocket (T47F, I177L, V319A and L405I) that are important for delicate substrate positioning of different chain-length fatty acids and thus the decarboxylation versus hydroxylation chemoselectivity, in particular for the mid-chain fatty acids (C₈-C₁₂). In addition, the three new decarboxylases exhibited optimal catalytic activity and stability at a salt concentration of 0.5 M, and were thus classified as moderate halophilic enzymes.

CONCLUSION

The P450 fatty acid decarboxylases OleT_JE, OleT_JH, OleT_SQ and OleT_SA belong to a novel group of moderate halophilic P450 enzymes. OleT_JH from Jeotgalicoccus halophilus shows the decarboxylation activity, kinetic parameters, as well as salt tolerance and stability that are comparable to OleT_JE. Site-directed mutagenesis of several key amino acid residues near substrate-binding pocket provides important guidance for further engineering of these P450 fatty acid decarboxylases that hold promising application potential for production of α-olefin biohydrocarbons.

Eggshells as a source for occupational exposure to airborne bacteria in hatcheries

Occupational exposure to high concentrations of airborne bacteria in poultry production is related to an increased risk of respiratory disorders. However, potential sources and formation of hatchery bioaerosols are rarely characterized. In this study, bacterial multiplication on fresh shell fragments from turkey hatching eggs under conditions present in a hatcher incubator was investigated. A 10⁵-fold amplification was observed both by colony count and total cell count gaining 4 × 10⁷ cfu/cells per gram eggshell within 30 hr of incubation. Furthermore, the bacterial community present on eggshells was analyzed by generation of 16S rRNA gene clone libraries and identification of eight isolates. RFLP analysis revealed no shift in community composition during incubation and Enterococcus faecalis and Enterococcus gallinarum were found as the predominant species on turkey eggshells, both have been classified as risk group 2 microorganisms (German TRBA 466). Since Enterococcus spp. were found as predominant species on turkey eggshells, contribution of this genus to bioaerosol formation was demonstrated. During different work activities with poult and eggshell handling concentrations of airborne enterococci up to 1.3 × 10⁴ cfu m^-3 were detected. In contrast, no enterococci were identified at a day without poult or eggshell processing. In conclusion, turkey hatching eggs carry a viable specific microflora from breeder flocks to hatcheries. After hatching of turkey poults, hatcher incubators and eggshell fragments provide appropriate conditions for excessive bacterial growth. Thus, high bacterial loads on eggshell fragments are a source of potential harmful bioaersols caused by air flows, poult activity, and handling of equipment.

Characterization by culture-dependent and culture-independent methods of the bacterial population of suckling-lamb packaged in different atmospheres

This study offers insight into the dynamics of bacterial populations in fresh cuts of suckling lamb under four different atmospheric conditions: air (A), and three Modified Atmosphere Packaging (MAP) environments, 15%O2/30%CO2/55%N2 (C, commercial), 70%O2/30%CO2 (O), and 15%O2/85%CO2 (H) for 18 days. Microbial analyses by both conventional methods and PCR-DGGE were performed. Controversial and surprising results emerged from comparing both methods in relation to the genus Pseudomonas. Thus, conventional methods detected the presence of high numbers of Pseudomonas colonies, although PCR-DGGE only detected this genus in air-packaged samples. PCR-DGGE detected higher microbial diversity in the control samples (A) than in the modified atmospheres (C, O, H), having atmosphere H the fewest number of species. Brochothrix thermosphacta, LAB (Carnobacterium divergens and Lactobacillus sakei), and Escherichia spp. were detected in all the atmospheres throughout storage. Moreover, previously undescribed bacteria from lamb meat such as Enterobacter hormaechei, Staphylococcus equorum and Jeotgalicoccus spp. were also isolated in this study by DGGE. Additionally, qPCR analysis was used to detect and characterize strains of Escherichia coli. Virulence genes (stx1, stx2 and eae) were detected throughout storage in 97% of the samples. A high CO2 atmosphere was the most effective packaging combination doubling storage time in comparison with commercial atmosphere.