Antibiotic exposure alters the honeybee gut microbiota and may interfere with the honeybee behavioral caste transition.

Behavioral division is essential for the sustainability and reproduction of honeybee populations. While accumulating evidence has documented that antibiotic exposure interferes with bee behavioral divisions, how the gut microbiome, host physiology, and genetic regulation are implicated in this process remains understudied. Here, by constructing single-cohort colonies, we validated that the gut microbiota varied in composition between age-matched nurse and forager bees. Perturbing the gut microbiota with a low dose of antibiotic retained the gut bacterial size, but the structure of the microbial community continuously diverged from the control group after antibiotic treatment. Fewer foragers were observed in the antibiotic groups in the field experiment. A combinatorial effect of decreased gut metabolic gene repertoires, reduced brain neurotransmitter titers, and downregulated brain immune genes could potentially be related to behavioral tasks transition delay. This work indicates that the disturbance to both the gut microbiome and host physiologies after antibiotic exposure may have implications on social behavior development, highlighting the need for further research focusing on antibiotic pollution threatening the honeybee population's health.

Potential modulating effects of Allium mongolicum regel ethanol extract on rumen fermentation and biohydrogenation bacteria of dairy cows in vitro.

The objective of this study was to evaluate the potential modulating effects of Allium mongolicum regel ethanol extract (AME) on rumen fermentation and biohydrogenation (BH) bacteria in vitro. Four Holstein cows were used as donors for the rumen fluid used in this study. In experiment 1, five treatments (supplemented with 0 mg/g, 1 mg/g, 2 mg/g, 3 mg/g, and 4 mg/g of AME based on fermentation substrate, respectively) were conducted to evaluate the effects of different levels of AME on fermentation status in vitro. The results showed that after 24 h of fermentation, MCP was reduced with AME supplementation (p < 0.05), and the multiple combinations of different combinations index (MFAEI) value was the highest with 3 mg/g of AME. In experiment 2, six treatments were constructed which contained: control group (A1); the unsaturated fatty acid (UFA) mixture at 3% concentration (A2); the mixture of A2 and 3 mg/g of AME (A3); 3 mg/g of AME (A4); the UFA mixture at 1.5% concentration (A5); the mixture of A5 and 3 mg/g of AME (A6). The abundance of bacterial species involved in BH was measured to evaluate the potential modulating effect of AME on rumen BH in vitro. Compared with the A1 group, the A3, A4, and A6 groups both showed significant decreases in the abundance of rumen BH microbial flora including Butyrivibrio proteoclasticus, Butyrivibrio fibrisolvens, Ruminococcus albus and Clostridium aminophilum (p < 0.01). The A3 group was less inhibitory than A4 in the abundance of B. proteoclasticus, B. fibrisolvens, and R. albus, and the inhibitory effect of the A6 group was higher than that of A4. In conclusion, the supplementation with 3 mg/g of AME could modulate the rumen fermentation and affect BH key bacteria, which suggests that AME may have the potential to inhibit the rumen BH of dairy cows.

Transcriptome analysis reveals candidate genes of the synthesis of branched-chain fatty acids related to mutton flavor in the lamb liver using Allium mongolicum Regel extract.

The objective of this study was to identify candidate genes via which Allium mongolicum Regel ethanol extract (AME) affects the synthesis of branched-chain fatty acids (BCFAs) related to mutton flavor by transcriptome analysis in the lamb liver. Thirty male Small-tailed Han sheep (3 mo old; 33.6 ± 1.2 kg) were randomly divided into two groups and fed for 75 d with a basal diet containing no AME (CON, control group) or 2.8 g·lamb-1·d-1 AME (AME group). Twelve sheep, CON (n = 6) and AME (n = 6), were selected for slaughter at the end of the trial period, and liver samples were subsequently collected. There was no difference in 4-ethyloctanoic acid content among treatments. The 4-methyloctanoic acid and 4-methylnonanoic acid levels were significantly lower in the AME group than in the CON group (P < 0.05). Furthermore, 461 differentially expressed genes (DEGs) were identified between the CON and AME groups, of which 182 were upregulated and 279 were downregulated in the AME group. The DEGs were enriched in three pathways, namely, glutathione metabolism, ECM-receptor interaction, and steroid hormone biosynthesis, as determined by the Kyoto Encyclopedia of Genes and Genomes pathway analysis. Finally, CYP2B6, ACOT12, THEM4, ACSF2, LPIN1, and ADCY4 were identified as candidate genes that might be involved in regulating the BCFAs synthesis in the sheep liver.

Mutton is characterized by a typical species-related flavor named "mutton flavor," which is mainly associated with branched-chain fatty acids (BCFAs), such as 4-methyloctanoic acid, 4-ethyloctanoic acid, and 4-methylnonanoic acid. Previous studies demonstrated that Allium mongolicum Regel ethanol extract (AME) reduced the concentration of BCFAs in the muscle and adipose tissues of lambs. The liver is a primary metabolic organ in mammals and is involved in the metabolism of BCFAs. In the present study, we investigated the influences of AME on the concentration of BCFAs and the transcriptomic profile in the lamb liver. Supplementation of lamb diet with AME reduced the concentration of BCFAs in the liver. We also found six candidate genes related to the synthesis of BCFAs from differentially expressed genes in the liver. The findings of this work contribute to a better understanding of the effect of AME on the synthesis of BCFAs in the liver of lambs.

Honeybee gut Lactobacillus modulates host learning and memory behaviors via regulating tryptophan metabolism.

Honeybees are highly social insects with a rich behavioral repertoire and are a versatile model for neurobiological research. Their gut microbiota comprises a limited number of host-restricted bacterial phylotypes that are important for honeybee health. However, it remains unclear how specific gut members affect honeybee behaviors. Here, we find that antibiotic exposure disturbs the gut community and influences honeybee phenotypes under field conditions. Using laboratory-generated gnotobiotic bees, we show that a normal gut microbiota is required for olfactory learning and memory abilities. Brain transcriptomic profiling reveals distinct brain gene expression patterns between microbiota-free and conventional bees. Subsequent metabolomic analyses of both hemolymph and gut samples show that the microbiota mainly regulates tryptophan metabolism. Our results indicate that host-specific Lactobacillus strains promote memory behavior by transforming tryptophan to indole derivatives that activate the host aryl hydrocarbon receptor. Our findings highlight the contributions of specific gut members to honeybee neurological processes, thus providing a promising model to understand host-microbe interactions.

Effects of the Dietary Inclusion of Allium mongolicum Regel Extract on Serum Index and Meat Quality in Small-Tailed Han Sheep.

The aim of this study was to evaluate the effects of Allium mongolicum Regel ethanol extract (AME) on the serum index and meat quality of lambs. A total of 30 male Small-tailed Han sheep (3 months old) with an average weight of 33.60 ± 1.23 kg were divided randomly into one of two groups: the control group (CON) was offered a basal diet, and the AME group was offered a basal diet with supplementation 2.8 g·lamb−1·day−1 AME. The trial lasted for 75 days. AME supplementation significantly decreased the concentration of triglyceride and total cholesterol (p < 0.05), and tended to lower the concentration of non-esterified fatty acids (0.05 < p < 0.1), but significantly increased the concentration of high-density lipoprotein, leptin, and insulin (p < 0.05) in the serum of lambs. AME also decreased cooking losses and shear force and increased the content of intramuscular fat in the longissimus dorsi (LD) muscle of lambs (p < 0.05). In addition, there was no difference in the composition of hydrolyzed protein amino acids in the LD muscle among treatments (p > 0.05). However, AME changed the composition of free amino acids and promoted MUFA and PUFA deposition in the LD muscle of the lambs. These findings indicate that a diet supplemented with AME may improve the lipid metabolic capacity and meat quality of lambs.

Tissue-specific regulatory mechanism of LncRNAs and methylation in sheep adipose and muscle induced by Allium mongolicum Regel extracts.

Allium mongolicum Regel (A. mongolicum) is a perennial and xerophytic Liliaceous allium plant in high altitude desert steppe and desert areas. Feeding A. mongolicum greatly reduced unpleasant mutton flavor and improves meat quality of sheep. We analyzed epigenetic regulatory mechanisms of water extracts of A. mongolicum (WEA) on sheep muscle and adipose using RNA-Seq and whole-genome Bisulfite sequencing. Feeding WEA reduced differentially expressed genes and long non-coding RNAs (lncRNAs) between two tissues but increased differentially methylation regions (DMRs). LncRNA and DMR targets were both involved in ATP binding, ubiquitin, protein kinase binding, regulation of cell proliferation, and related signaling pathways, but not unsaturated fatty acids metabolism. Besides, tissue specific targets were involved in distinct functional annotations, e.g., Golgi membrane and endoplasmic reticulum for muscle lncRNA, oxidative phosphorylation metabolism for adipose lncRNA, dsRNA binding for muscle DMRs. Epigenetic regulatory networks were also discovered to discovered essential co-regulated modules, e.g., co-regulated insulin secretion module (PDPK1, ATP1A2, CACNA1S and CAMK2D) in adipose. The results indicated that WEA induced distinct epigenetic regulation on muscle and adipose to diminish transcriptome differences between tissues, which highlights biological functions of A. mongolicum, tissue similarity and specificity, as well as regulatory mechanism of mutton odor.