Phage therapy typically fails when bacteria rapidly evolve resistance, yet the inevitable fitness costs of escape mutants remain underexploited. In this study, an iterative and targeted phage-cocktail formulation strategy (ITPFS) was presented and developed. A potent lytic phage, PHZ055, was firstly isolated against a colistin-resistant Salmonella Pullorum strain. Co-cultured until resistant mutants emerged, a second lytic phage, PYW047_3, was screened for the resistant variant. The two phages were then combined as a cocktail. Results showed that bacterial growth was strongly suppressed and the emergence of resistance was markedly delayed. Receptor identification revealed that both phages use lipopolysaccharide (LPS) as a receptor, but at distinct sites: PHZ055 targets WaaL, and PYW047_3 targets WaaP. Mutation of WaaL was recently shown to be responsible for the loss of polymerized O-antigen units and thereby exposed the PYW047_3 binding region, indicating that phage cocktails targeting distinct receptor sites can be directionally screened. Moreover, mutants that escaped the two phages not only incurred a growth cost but also exhibited a 32-fold increase in colistin sensitivity. Combining the two phages together with 1/4 MIC colistin almost eradicated all bacteria within 24 h. In all, our study successfully provides a repeatable strategy that incorporates adaptive trade-offs to boost therapeutic efficacy.

Tibial dyschondroplasia (TD) is a metabolic cartilage disorder in fast-growing broilers, which severely impacts poultry welfare and productivity. Baicalin is a bioactive flavonoid with anti-inflammatory and antioxidant properties; its therapeutic potential has not been studied for TD. This study paves the way in elucidating baicalin's chondroprotective mechanism through CDH11/Wnt/(3-catenin signaling and evaluating its therapeutic efficacy. Notably, baicalin significantly improved TD broilers' symptoms (e.g., slow weight-gain, reduced feed intake) and up-regulated tibia morphometrics. Special staining showed abnormal cartilage enlargement in TD and self-healing groups, while histomorphometry indicated restored tibial trabecular architecture in treated groups. Mechanistically, the cartilage development-related genes CDH11, RUNX2, and alkaline phosphatase (ALP) were significantly upregulated in the baicalin-treated group, and pivotal molecular factors in the Wnt/(3catenin-dependent signaling axis, which are involved in cartilage development, were up-regulated or down-regulated. These findings establish that baicalin mitigates TD pathogenesis through CDH11-dependent activation of canonical Wnt signaling, promoting chondrocyte maturation and skeletal remodeling, which will provide both mechanistic insights into avian skeletal metabolism and a clinically translatable strategy for metabolic bone diseases.

Microplastics (MPs) pollution is a growing global environmental concern. MPs serve as ecological niches for microbial communities, which may accelerate the spread of antibiotic resistance genes (ARGs), posing risks to the breeding industry. While studies on MPs in aquatic organisms are common, research on farmed poultry is limited. This study investigates MPs in poultry farm environments and waterfowl intestines for the first time. MPs were isolated via density separation and analyzed for characterization in soil, pond water, and waterfowl intestines. Metagenomics was used to investigate the association between environment MPs colonized-microbiota and waterfowl gut microbiota. Our findings reveal that MPs are abundant in soil (6.75 ± 2.78 items/g d.w.), pond water (0.94 ± 0.28 items/g w.w.), and poultry intestines (45.35 ± 19.52 items/g w.w.), primarily appearing as fragmented particles sized 20-50 μm. MPs abundance in intestines correlates with environmental levels. Colonized-microbiota on MPs are linked to poultry intestinal microbiota, with greater diversity and microbial functions. Network analysis reveals that Corynebacterium plays a key role in MPs and poultry intestinal. Polymyxin resistance exhibits high clustering. Procrustes analysis reveals correlations between MPs, bacteria, and ARGs in the farming environment. Overall, MPs in poultry farms may facilitate pathogen and ARGs transmission, posing risks to animal gut health.

The environmental impacts of antibiotics in sediments, which are a key problem restricting the sustainable development of aquaculture, have been reported extensively. Biological denitrification is a low-cost means to remediate environment. To clarify the the remediation behavior of Paracoccus denitrificans in sewage environment, we studied the changes of bacterial community in sediments polluted by florfenicol after inoculation with P. denitrificans through amplicon technology. Our results showed that P. denitrificans continuously enriched some antibiotic-responsive small RNAs (sRNAs) in promotion of florfenicol degradation, making the abundance of denitrifying functional genes tend to be normalized. Florfenicol and NH4+-N are the main factors affecting bacterial communities regarding the results of redundancy analysis (RDA) and pearson's correlation analysis. In the denitrification-related functional categories, the function of nitrate reduction in the community was obviously enhanced. Furthermore, the risk of pathogen infection induced by florfenicol was reduced. In conclusion, our study exhibited the ability of strain P. denitrificans to degrade florfenicol and bioremediate, which provided a theoretical basis for the application of P. denitrificans in aquaculture industry.

Riemerella anatipestifer, an important waterfowl pathogen, causes severe economic losses because of limited prevention and control methods. We aimed to characterize the prophages of R. anatipestifer and explore their role in lysogenic conversion and fitness cost to host bacteria based on the interactive infection of 110 wild-type strains and ATCC 11845. The temperate phages PJA1, PJO17, PJR4, PJL1, and PJX6 were isolated from clinical strains and showed various lytic abilities, high similarity between different Riemerella phages, and stable properties in transmission electron microscopy, temperature sensitivity, and one-step growth curve detection. To study the effects of lysogeny, we developed five lysogenic strains by integrating phages into the genome of JW1, a wild-type and prophage-absent strain of R. anatipestifer that is particularly susceptible to phage infection. The spontaneous induction frequency of the lysogen strains reached approximately 4-log, showing resistance to each other. Genomic analysis revealed high similarity to the first characterized Riemerella phage, RAP44, particularly in structural gene modules. Lysogens exhibited resistance to superinfection by prophages, similar to the reference strain ATCC 11845. Compared to JW1, lysogens showed consistent growth curves and colony morphology but were significantly thicker and shorter in scanning electron microscopy images. The lysogenic conversion process reduced the minimum inhibitory concentration of rifampin for lysogen JW1_PJA1 and JW1_PJO17 to 1/4 and 1/8 of that observed in the strain JW1, respectively, and decreased the MIC of florfenicol for lysogen JW1_PJR4 to half of the original value. Genomic comparisons revealed prophage integration and sequence rearrangement in lysogen genomes under the action of integrase. Co-culture experiments demonstrated that sensitive JW1 could be lysogenized by phages that were spontaneously induced from lysogens. Given the high prevalence of prophages in R. anatipestifer and no significant growth defect under laboratory conditions, lysogenic conversion appears to be a natural adaptation of this pathogen. By elucidating how prophages affect R. anatipestifer resistance and fitness, our findings provide a foundation for harnessing these interactions to design effective phage-based control strategies.

Riemeralla anatipestifer, a predominant bacterium with multidrug resistance, has caused tremendous economic losses in the poultry farming industry. However, there are few studies on its identification, pathogenic mechanisms, and virulence factors and effective and systematic prevention and control strategies. The emergence and spread of antibacterial resistance has prompted increased focus on R. anatipestifer. However, studies on the mechanisms underlying gene aggregation and dissemination are lacking. This review summarizes recent studies on R. anatipestifer and explores its epidemiology, pathobiology, serotype classification, and preventive and treatment measures. Our findings illuminate the characteristics of virulence-related and drug resistance factors that have pivotal roles in the pathogenesis of R. anatipestifer infection. This study provides a comprehensive reference and guidance for in-depth research on R. anatipestifer.

Quorum sensing potentially helps microorganisms adapt to antibiotic stress encountered in the environment. This experiment investigated the effect of acyl homoserine endolipid-like signaling molecules on microbial antibiotic resistance gene structures in aqueous sediments under florfenicol stress. Additional acyl homoserine endolipid-like signaling molecules (AHLs) alter the structure of multidrug resistance genes in florfenicol-stressed sediments, particularly the multidrug resistance efflux pump gene family. Prophages and integrative and conjugative elements (ICEs) determined the resistance genes structure, and pathways related to mobile genetic elements (MGEs) transfer may play an essential role in this process. The practical application of AHLs to regulate quorum sensing systems may alter bacterial stress responses to environmental florfenicol residues, thereby reducing the development of antibiotic resistance in the environment.

Antibiotic-resistant bacteria are current threats to available antibiotic therapies, and this has renewed interest in the therapeutic use of phage as an alternative. However, development of phage resistance has led to unsuccessful therapeutic outcomes. In the current study, we applied phage training to minimize bacterial phage resistance and to improve treatment outcome by adapting the phage to their target hosts during co-evolution. We isolated and characterized a novel Pseudomonas aeruginosa N4-like lytic phage (PWJ) from wastewater in Yangzhou, China. PWJ is a double-stranded DNA podovirus that can efficiently lyse the model strain ATCC 27,853 and opportunistic pathogen PAO1. Genome sequencing of PWJ revealed features similar to those of the N4-like P. aeruginosa phage YH6. We used PWJ to screen for an evolved trained phage (WJ_Ev14) that restored infectivity to PWJ phage bacterial resisters. BLASTN analysis revealed that WJ_Ev14 is identical to its ancestor PWJ except for the amino acid substitution R1051S in its tail fiber protein. Moreover, phage adsorption tests and transmission electron microscopy of resistant bacteria demonstrated that the R1051S substitution was most likely the reason WJ_Ev14 could re-adsorb and regain infectivity. Furthermore, phage therapy assays in vitro and in a mouse P. aeruginosa lung infection model demonstrated that PWJ treatment resulted in improved clinical results and a reduction in lung bacterial load whereas the joint phage cocktail (PWJ+ WJ_Ev14) was better able to delay the emergence of resister bacteria. The phage cocktail (PWJ +WJ_Ev14) represents a promising candidate for inclusion in phage cocktails developed for clinical applications.

Antimicrobial resistance (AMR) in clinically priority pathogensis now a major threat to public health worldwide. Phages are bacterial parasites that efficiently infect or kill specific strains and represent the most abundant biological entities on earth, showing great attraction as potential antibacterial therapeutics in combating AMR. This review provides a summary of phage-inspired strategies to combat AMR. We firstly cover the phage diversity, and then explain the biological principles of phage therapy that support the use of phages in the post-antimicrobial era. Furthermore, we state the versatility methods of phage therapy both from direct access as well as collateral access. Among the direct access approaches, we discuss the use of phage cocktail therapy, phage-encoded endolysins and the bioengineering for function improvement of used phages or endolysins. On the other hand, we introduce the collateral access, including the phages antimicrobial immunity combined therapy and phage-based novel antibacterial mimic molecules. Nowadays, more and more talented and enthusiastic scientist, doctors, pharmacists, media, authorities, and industry are promoting the progress of phage therapy, and proposed more phages-inspired strategy to make them more tractable to combat AMR and benefit more people, more animal and diverse environment in "one health" framework.

【Objective】The ecotoxic effects of florfenicol and copper（Cu） residues on soil nitrogen-fixing bacteria were studied to provide a basis for evaluating the environmental risks of veterinary drugs.【Method】A dominant nitrogen-fixing bacterium RpEC2071 was isolated from peanut root enclosure and treated under florfenicol and Cu stress. We set the blank group（0 μg/mL）, florfenicol group（40 μg/mL）, Cu group（200μg/mL） and mixed group（flufenicol 40 μg/mL, Cu 200 μg/mL）, and collected samples at multiple time points after dosing. The phenol-sulfuric acid method and 96-well microplate method were used to study the effects of florfenicol and Cu alone or in combination on the production of extracellular polysaccharides and biofilm formation of nitrogen-fixing bacterium. RT-qPCR was used to determine nitrogen-fixing bacterium biofilm formation and the mRNA expression levels of nitrogen fixation-related genes.【Result】Florfenicol and Cu alone promoted the formation of biofilms, and the biofilm formation capacity of both was about twice that of the blank group. Under mixed stress, the biofilm formation was inhibited, and the biofilm formation capacity of the blank group was 3.1 times that of it. The results of extracellular polysaccharide secretion were basically consistent with the results of the determination of biofilm formation ability. Biofilm-related genes were significantly positively correlated with nitrogen metabolism regulatory genes, and the addition of florfenicol and Cu changed the expression levels of genes such as fli Q, ntr X and nnr R, and it would produce synergistic or antagonistic effects after the combination treatment of florfenicol and Cu.【Conclusion】The individual or combined stress of florfenicol and Cu affects the expression of biofilm-related genes in nitrogen-fixing bacteria RpEC2071, which in turn affects its ability to form biofilm. This research reveals the ecotoxic potential of veterinary drugs and heavy metal residue stresses on soil nitrogen-fixing bacteria, using florfenicol and Cu as examples. As a result, this can lead to the impairment of the nitrogen-fixing ecosystem in soil.

近年来,中国宠物行业快速发展,宠物医院数量不断增加,带来宠物医疗人才一直处于紧缺的局面,但是高校兽医专业毕业生选择从事宠物临床诊疗工作的比例却非常低.因此,本文主要就高校兽医专业宠物医疗人才培养论题,从加强高校兽医专业宠物临床教学工作、引导高校兽医学生主动了解与学习宠物医疗知识、吸引高校兽医学生主动到宠物医院实践学习与工作等三个方面展开讨论,以期吸引更多的兽医专业毕业生选择宠物临床诊疗工作,促使中国宠物临床诊疗行业健康稳定与可持续发展.

The P1-like phage plasmid (PP) has been widely used as a molecular biology tool, but its role as an active accessory cargo element is not fully understood. In this study, we provide insights into the structural features and gene content similarities of 77 P1-like PPs in the RefSeq database. We also describe a P1-like PP carrying a blaCTX- M-55 gene, JL22, which was isolated from a clinical strain of Escherichia coli from a duck farm. P1-like PPs were very similar and conserved based on gene content similarities, with only eight highly variable regions. Importantly, two kinds of replicon types, namely, IncY and p0111, were identified and can be used to specifically identify the P1-like phage. JL22 is similar to P1, acquiring an important foreign DNA fragment with two obvious features, namely, the plasmid replication gene repA9 (p0111) replacing the gene repA (IncY) and a 4,200-bp fragment mobilized by IS1380 and IS5 and containing a blaCTX- M-55 gene and a trpB gene encoding tryptophan synthase (indole salvaging). The JL22 phage could be induced but had no lytic capacities. However, a lysogenic recipient and intact structure of JL22 virions were observed, showing that the extended-spectrum b- lactamase blaCTX- M-55 gene was successfully transferred. Overall, conserved genes can be a good complement to improve the identification efficiency and accuracy in future screening for P1-like PPs. Moreover, the highly conserved structures may be important for their prevalence and dissemination. IMPORTANCE As a PP, P1 DNA exists as a low-copy-number plasmid and replicates autonomously with a lysogenization style. This unique mode of P1-like elements probably indicates a stable contribution to antibiotic resistance. After analyzing these elements, we show that P1-like PPs are very similar and conserved, with only eight highly variable regions. Moreover, we observed the occurrence of replicon IncY and p0111 only in the P1-like PP community, implying that these conserved regions, coupled with IncY and p0111, can be an important complement in future screening of P1-like PPs. Identification and characterization of JL22 confirmed our findings that major changes were located in variable regions, including the first detection of blaCTX- M-55 in such a mobile genetic element. This suggests that these variable regions may facilitate foreign DNA mobilization. This study features a comprehensive genetic analysis of P1-like PPs, providing new insights into the dissemination mechanisms of antibiotic resistance through P1 PPs.

Paracoccus denitrificans can adapt to complex environmental changes and sRNAs play crucial roles during this process. This work aim to identify antibiotic-induced sRNA that regulated denitrification and explored its potential for functional enhancement of this process. Target prediction indicated complementary base pairing between the denitrifying gene nosZ and the sRNA Pda200. Anaerobic culture of P. denitrificans ATCC 19367 in the presence of florfenicol (FF) resulted in significant decreases in nosZ and Pda200 gene expression (p < 0.01). Two additional denitrifiers isolated from contaminated sediment were co-cultured with ATCC 19367 to generate a consortium. And an inducible Pda200 expression strain was also added. The results revealed that Pda200 significantly enhanced napA, napB and norB expression in different types of denitrifiers under FF condition (p < 0.05 similar to 0.001). This study identified the sRNA Pda200 as a novel positive regulator of denitrification, which may realize the efficient treatment of antibiotic-contaminated wastewater by microbial agents.

鲍曼不动杆菌(Acinetobacterbaumanii,Ab)是一类广泛存在于自然界的革兰氏阴性条件致病菌,是目前引起医院感染的最重要的致病菌之一.随着抗生素的大量使用,导致Ab耐药情况日益严峻,大大增加了治疗成本.研究表明,动物临床病例中由于细菌引起感染的比例不断上升,其中耐药Ab从兽医临床标本中分离出来的频率也越来越高.人类医学临床上已经证明Ab具有广泛的多重耐药性和传播风险特征,然而对动物源Ab缺乏关注令人担忧.因此,通过对Ab在动物中的流行病学和耐药性特征进行综述,以期为公共卫生安全预警,为动物源Ab耐药性监测提供依据.

Brucella can inhabit hostile environments, including osmotic stress. How Brucella responds collectively to osmotic stress is largely unexplored, particularly in spatially structured communities such as a biofilm. To gain insight into this growth mode, we set out to characterize the Brucella melitensis 16M biofilm, describe its phenotype, and carry out a comparative transcriptomic analysis between biofilms under osmotic stress and control conditions. We determined that the bacteria challenged with 1.5 M NaCl had a reduced ability to aggregate and form clumps and develop a biofilm; however, the salt stress promoted the release of the outer membrane vesicles from the biofilm. Together with the genotypical response to osmotic stress, we identified 279 differentially expressed genes in B. melitensis 16M grown under osmotic conditions compared with control conditions; 69 genes were upregulated and 210 downregulated. Under osmotic stress, the main changed genes of biofilm were predicted to be involved in flagellar assembly, cell envelope, translation, small RNA regulation, transport and binding proteins, and energy metabolism. In addition, the ABC transporter was enriched in the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. We highlight 12 essential ABC transporter genes associated with a bacterial response to osmotic stress at the biofilm stage, including one specific locus, BME_RS12880, mediating betaine accumulation in biofilms to eliminate osmotic stress. The current study results can help researchers gain insights into B. melitensis 16M biofilm adaptation to osmotic stress and provide information for developing intervention strategies to control Brucella.

Few studies have characterized the microbial community and metabolite profile of solid food waste fermented products from centralized treatment facilities, which could potentially be processed into safe animal feeds. In this study, 16S rRNA gene sequencing and liquid/gas chromatography-mass spectrometry were conducted to investigate the bacterial community structure and metabolite profile of food waste samples inoculated with or without 0.18% of a commercial bacterial agent consisting of multiple unknown strains and 2% of a laboratory-made bacterial agent consisting of Enterococcus faecalis, Bacillus subtilis and Candida utilis. Our findings indicated that microbial inoculation increased the crude protein content of food waste while reducing the pH value, increasing lactic acid production, and enhancing aerobic stability. Microbial inoculation affected the community richness, community diversity, and the microbiota structure (the genera with abundances above 1.5% in the fermentation products included Lactobacillus (82.28%) and Leuconostoc (1.88%) in the uninoculated group, Lactobacillus (91.85%) and Acetobacter (2.01%) in the group inoculated with commercial bacterial agents, and Lactobacillus (37.11%) and Enterococcus (53.81%) in the group inoculated with homemade laboratory agents). Microbial inoculation reduced the abundance of potentially pathogenic bacteria. In the metabolome, a total of 929 substances were detected, 853 by LC-MS and 76 by GC-MS. Our results indicated that inoculation increased the abundance of many beneficial metabolites and aroma-conferring substances but also increased the abundance of undesirable odors and some harmful compounds such as phenol. Correlation analyses suggested that Leuconostoc, Lactococcus, and Weissella would be promising candidates to improve the quality of fermentation products. Taken together, these results indicated that inoculation could improve food waste quality to some extent; however, additional studies are required to optimize the selection of inoculation agents.

Antimicrobial agents enter the ecological environment through animal excreta and disrupt metabolism in environmental microorganisms. Quorum sensing (QS) can help bacteria adapt to their surroundings. To explore how acyl-homoserine lactone (AHL) can adjust the influence of florfenicol on nitrogen cycling and methane metabolism in anaerobic fermentation, a small indoor thermostatic anaerobic fermentation model was established by adding exogenous acylated homoserine lactone (AHL) signal molecules with florfenicol as the stress factor. Through bacterial function prediction by PICRUST, we found that the addition of AHL further increased the promotion of methanogenesis_by_CO2_reduction_with_H2 and hydrogenotrophic methanogenesis by florfenicol. Before the third sampling, florfenicol significantly inhibited the enrichment of the denitrification pathway microbiota, whereas the addition of AHL significantly promoted the enrichment of the denitrification pathway microbiota. Functional annotation showed that florfenicol exposure stress significantly affected nitrogen and methane metabolism, and the addition of AHLs reduced the response of functional genes to florfenicol. All nitrogen cycling enzymes with significantly different abundances in treatment groups were substantially associated with methane-metabolizing enzymes. Glutamate metabolism is significant in the process of anaerobic fermentation, and is a correlation point between nitrogen and methane metabolism. In our experiment, AHL was the influencing factor at the highest latitude that directly regulates the metabolism of NO3--N and the degradation process of florfenicol. The addition of AHL curbed the inhibitory effect of florfenicol on some functional microbiota, improved the stability of fermentation microbiota, and weakened the impact of antibiotic residues by improving its degradation efficiency.

兽医药理学作为动物医学专业的一门基础学科,知识点冗杂分散,晦涩难懂,难以激发学生的自主学习热情.但它同时是一门应用性极强的学科,是动物临床诊疗用药的基础课程.因此在实际教学中需要运用多种教学方法提高兽医药理学的教学效果.文章提出目前兽医药理学教学过程中遇到的问题,包括教学方式单调、学生缺乏兴趣、课程设置单一以及教授内容缺乏实用性等.针对以上现状,文章探讨将云课堂引入兽医药理学教学过程、开展兽医药理学相关课外活动、互动式教学、动画教学、案例驱动和游戏教学等手段来提升学生的学习热情,使学生学有所得,学以致用,使该门课程的效益最大化,解决当前兽医药理教学痛点.

Huge number of antibiotic resistance genes (ARGs) have been widely detected in phage genomes from anthropogenic environment or animal farms, whereas little is known about the dynamic changes of phage contribution to resistance under a feedlot wastewater treatment facility (WTF) pressure. Here, a metagenomics method was used to characterize the sewage phageome and identifies the antibiotic resistome. The results showed that the phage families of Siphoviridae, Myoviridae, and Podoviridae were always the most dominant. Analysis of ARGs carried by bacterial and phages showed that MLS and tetracycline resistance genes always had the highest abundances and the other ARG types also have a fixed hierarchy, showing that there is no significant change in overall ARGs abundance distribution. However, an extensively cored antibiotic resistome were specifically identified in aerobic environment. ARGs encoding ribosomal protection proteins, especially for the ARG subtypes lsaE, tet44, tetM, tetP, macB, MdlB and rpoB2, were more inclined to be selected by phages, suggesting that a more refined mechanism, such as specialized transduction and lateral transduction, was probably involved. In all, these results suggest that monitoring of dynamic changes of phage contribution to resistance should be given more attention and ARGs-carrying phage management should focus on using technologies for controlling cored ARGs rather than only the overall distribution of ARGs in phages.

Heavy metal pollution can serve as a selective pressure for antibiotic resistance genes in polluted environments. Anaerobic fermentation, as a recommended wastewater treatment method, is an effective mitigation measure of antibiotic resistance diffusion. To explore the influence of copper on anaerobic fermentation, we exposed the fermentation substrate to copper in a laboratory setup. We found that the relative abundance of 8 genes (pcoD, tetT, tetA, tetB, tetO, qnrS, ermA and ermB) increased at the late stage of fermentation and their abundance was linked to copper content. Corynebacterium and Streptococcus were significantly positively correlated with ermA, ermB, tetA and tetB (P < 0.05). The relative abundance of tetT was significantly positively correlated with Terrisporobacter, Clostridium_sensu_stricto_1 and Turicibacter (P < 0.05). We screened 90 strains of copper resistant bacteria from blank, medium and high copper test groups on days 25, 31 and 37. The number of fragments carried by a single strain increased with time while intl1, ermA and ermB existed in almost all combinations of the multiple fragments we identified. The relative abundance of these three genes were linearly correlated with Corynebacterium and Streptococcus. The antibiotic resistance genes carried by class 1 integrons gradually increased with time in the fermentation system and integrons carrying ermA and ermB most likely contributed to host survival through the late stages of fermentation. The genera Corynebacterium and Streptococcus may be the primary carriers of such integrated mobile gene element and this was most likely the reason for their rebound in relative abundance during the late fermentation stages.