Arc1 and the microbiota together modulate growth and metabolic traits in Drosophila.

Perturbations to animal-associated microbial communities (the microbiota) have deleterious effects on various aspects of host fitness, but the molecular processes underlying these impacts are poorly understood. Here, we identify a connection between the microbiota and the neuronal factor Arc1 that affects growth and metabolism in Drosophila. We find that Arc1 exhibits tissue-specific microbiota-dependent expression changes, and that germ-free flies bearing a null mutation of Arc1 exhibit delayed and stunted larval growth, along with a variety of molecular, cellular and organismal traits indicative of metabolic dysregulation. Remarkably, we show that the majority of these phenotypes can be fully suppressed by mono-association with a single Acetobacter sp. isolate, through mechanisms involving both bacterial diet modification and live bacteria. Additionally, we provide evidence that Arc1 function in key neuroendocrine cells of the larval brain modulates growth and metabolic homeostasis under germ-free conditions. Our results reveal a role for Arc1 in modulating physiological responses to the microbial environment, and highlight how host-microbe interactions can profoundly impact the phenotypic consequences of genetic mutations in an animal host.

The influence of Acetobacter pomorum bacteria on the developmental progression of Drosophila suzukii via gluconic acid secretion.

Insects are rich in various microorganisms, which play diverse roles in affecting host biology. Although most Drosophila species prefer rotten fruits, the agricultural pest Drosophila suzukii attacks ripening fruits before they are harvested. We have reported that the microbiota has positive and negative impacts on the agricultural pest D. suzukii on nutrient-poor and -rich diets, respectively. On nutrient-poor diets, microbes provide protein to facilitate larval development. But how they impede D. suzukii development on nutrient-rich diets is unknown. Here we report that Acetobacter pomorum (Apo), a commensal bacterium in many Drosophila species and rotting fruit, has several detrimental effects in D. suzukii. Feeding D. suzukii larvae nutrient-rich diets containing live Apo significantly delayed larval development and reduced the body weight of emerged adults. Apo induced larval immune responses and downregulated genes of digestion and juvenile hormone metabolism. Knockdown of these genes in germ-free larvae reproduced Apo-like weakened phenotypes. Apo was confirmed to secrete substantial amounts of gluconic acid. Adding gluconic acid to the D. suzukii larval diet hindered larval growth and decreased adult body weight. Moreover, the dose of gluconic acid that adversely affected D. suzukii did not negatively affect Drosophila melanogaster, suggesting that D. suzukii is less tolerant to acid than D. melanogaster. Taken together, these findings indicate that D. suzukii is negatively affected by gluconic acid, which may explain why it prefers ripening fruit over Apo-rich rotting fruit. These results show an insect's tolerance to microbes can influence its ecological niche.

Overproduction of bacterial cellulose from Acetobacter xylinum BPR2001 using food industries wastes.

In this study, a cost-effective complex culture media containing molasses and corn steep liquor (CSL) was developed for the high production of bacterial cellulose (BC) by investigating the effect of four effective factors on BC production at three levels using Taguchi and combined methods. The predicted and actual values of BC production in optimal conditions by Taguchi and combined methods were 8.41 and 14.52 g/L, respectively. These results showed that the combined method was more suitable for predicting the optimal conditions in the optimization of BC production, the cost of developed culture medium was around 94% cost of HS medium preparation, molasses was the most effective factor in both experimental design methods, and initial pH adjustment had little impact on BC production. Then, the effect of inoculation conditions containing three factors of inoculation age, ethanol addition time, and agitation rate on the increase of BC production at three levels was investigated using the response surface methodology with the Box-Behnken design algorithm. Under the optimal conditions including inoculum age of 3 days, ethanol addition time of 10 days, and stirring speed of 100 rpm, the predicted and experimental results of BC production were 21.61 and 20.21 g/L, respectively. This is among the highest ever reported for BC production, which was achieved with a more cost-effective culture medium containing molasses and CSL.

Improving the alcohol respiratory chain and energy metabolism by enhancing PQQ synthesis in Acetobacter pasteurianus.

Pyrroloquinoline quinone (PQQ) is one of the important coenzymes in living organisms. In acetic acid bacteria (AAB), it plays a crucial role in the alcohol respiratory chain, as a coenzyme of alcohol dehydrogenase (ADH). In this work, the PQQ biosynthetic genes were overexpressed in Acetobacter pasteurianus CGMCC 3089 to improve the fermentation performance. The result shows that the intracellular and extracellular PQQ contents in the recombinant strain A. pasteurianus (pBBR1-p264-pqq) were 152.53% and 141.08% higher than those of the control A. pasteurianus (pBBR1-p264), respectively. The catalytic activity of ADH and aldehyde dehydrogenase increased by 52.92% and 67.04%, respectively. The results indicated that the energy charge and intracellular ATP were also improved in the recombinant strain. The acetic acid fermentation was carried out using a 5 L self-aspirating fermenter, and the acetic acid production rate of the recombinant strain was 23.20% higher compared with the control. Furthermore, the relationship between the PQQ and acetic acid tolerance of cells was analyzed. The biomass of recombinant strain was 180.2%, 44.3%, and 38.6% higher than those of control under 2%, 3%, and 4% acetic acid stress, respectively. After being treated with 6% acetic acid for 40 min, the survival rate of the recombinant strain was increased by 76.20% compared with the control. Those results demonstrated that overexpression of PQQ biosynthetic genes increased the content of PQQ, therefore improving the acetic acid fermentation and the cell tolerance against acetic acid by improving the alcohol respiratory chain and energy metabolism. ONE SENTENCE SUMMARY: The increase in PQQ content enhances the activity of the alcohol respiratory chain of Acetobacter pasteurianus, and the increase in energy charge enhances the tolerance of cells against acetic acid, therefore, improving the efficiency of acetic acid fermentation.

Metagenetic analysis of the bacterial diversity of Kazakh koumiss and assessment of its anti-Candida albicans activity.

Koumiss, a five-thousand-year-old fermented mare's milk beverage, is widely recognized for its beneficial nutrient and medicinal properties. The microbiota of Chinese and Mongolian koumiss have been largely characterized in recent years, but little is known concerning Kazakh koumiss despite this drink historically originates from the modern Kazakhstan territory. In addition, while koumiss is regarded as a drink with therapeutic potential, there are also no data on koumiss anti-Candida activity. In this context, the aims of the present study were to investigate the bacterial diversity and anti-Candida albicans activity of homemade Kazakh koumiss samples as well as fermented whey and cow's milk, derived from koumiss and propagated for several months. Koumiss bacterial communities were largely dominated by lactic acid bacteria including Lactobacillus sensu lato spp. (69% of total reads), Streptococcus (8.0%) and Lactococcus (6.1%), while other subdominant genera included Acetobacter (2.6%), Enterobacter (2.4%), and Klebsiella (1.5%). Several but not all koumiss samples as well as fermented whey and cow's milk showed antagonistic activities towards C. albicans. Linear discriminant effect size (LEfSe) analysis showed that their bacterial communities were characterized by a significantly higher abundance of amplicon sequence variants (ASV) belonging to the genus Acetobacter. In conclusion, this study allowed to identify the key microorganisms of Kazakh koumiss and provided new information on the possible underestimated contribution of acetic acid bacteria to its probiotic properties.

Chemical Synthesis of Acetobacter pasteurianus Lipid A with a Unique Tetrasaccharide Backbone and Evaluation of Its Immunological Functions.

Lipopolysaccharide (LPS), a cell surface component of Gram-negative bacteria, activates innate immunity. Its active principle is the terminal glycolipid lipid A. Acetobacter pasteurianus is a Gram-negative bacterium used in the fermentation of traditional Japanese black rice vinegar (kurozu). In this study, we focused on A. pasteurianus lipid A, which is a potential immunostimulatory component of kurozu. The active principle structure of A. pasteurianus lipid A has not yet been identified. Herein, we first systematically synthesized three types of A. pasteurianus lipid As containing a common and unique tetrasaccharide backbone. We developed an efficient method for constructing the 2-trehalosamine skeleton utilizing borinic acid-catalyzed glycosylation to afford 1,1'-α,α-glycoside in high yield and stereoselectivity. A common tetrasaccharide intermediate with an orthogonal protecting group pattern was constructed via [2+2] glycosylation. After introducing various fatty acids, all protecting groups were removed to achieve the first chemical synthesis of three distinct types of A. pasteurianus lipid As. After evaluating their immunological function using both human and murine cell lines, we identified the active principles of A. pasteurianus LPS. We also found the unique anomeric structure of A. pasteurianus lipid A contributes to its high chemical stability.

Exploring breast tissue microbial composition and the association with breast cancer risk factors.

BACKGROUND: Microbial dysbiosis has emerged as an important element in the development and progression of various cancers, including breast cancer. However, the microbial composition of the breast from healthy individuals, even relative to risk of developing breast cancer, remains unclear. Here, we performed a comprehensive analysis of the microbiota of the normal breast tissue, which was analyzed in relation to the microbial composition of the tumor and adjacent normal tissue. METHODS: The study cohorts included 403 cancer-free women (who donated normal breast tissue cores) and 76 breast cancer patients (who donated tumor and/or adjacent normal tissue samples). Microbiome profiling was obtained by sequencing the nine hypervariable regions of the 16S rRNA gene (V1V2, V2V3, V3V4, V4V5, V5V7, and V7V9). Transcriptome analysis was also performed on 190 normal breast tissue samples. Breast cancer risk score was assessed using the Tyrer-Cuzick risk model. RESULTS: The V1V2 amplicon sequencing resulted more suitable for the analysis of the normal breast microbiome and identified Lactobacillaceae (Firmicutes phylum), Acetobacterraceae, and Xanthomonadaceae (both Proteobacteria phylum) as the most abundant families in the normal breast. However, Ralstonia (Proteobacteria phylum) was more abundant in both breast tumors and histologically normal tissues adjacent to malignant tumors. We also conducted a correlation analysis between the microbiome and known breast cancer risk factors. Abundances of the bacterial taxa Acetotobacter aceti, Lactobacillus vini, Lactobacillus paracasei, and Xanthonomas sp. were associated with age (p < 0.0001), racial background (p < 0.0001), and parity (p < 0.0001). Finally, transcriptome analysis of normal breast tissues showed an enrichment in metabolism- and immune-related genes in the tissues with abundant Acetotobacter aceti, Lactobacillus vini, Lactobacillus paracasei, and Xanthonomas sp., whereas the presence of Ralstonia in the normal tissue was linked to dysregulation of genes involved in the carbohydrate metabolic pathway. CONCLUSIONS: This study defines the microbial features of normal breast tissue, thus providing a basis to understand cancer-related dysbiosis. Moreover, the findings reveal that lifestyle factors can significantly affect the normal breast microbial composition.

Acetobacter pomorum in the Drosophila gut microbiota buffers against host metabolic impacts of dietary preservative formula and batch variation in dietary yeast.

Gut microbiota are fundamentally important for healthy function in animal hosts. Drosophila melanogaster is a powerful system for understanding host-microbiota interactions, with modulation of the microbiota inducing phenotypic changes that are conserved across animal taxa. Qualitative differences in diet, such as preservatives and dietary yeast batch variation, may affect fly health indirectly via microbiota, and may potentially have hitherto uncharacterized effects directly on the fly. These factors are rarely considered, controlled, and are not standardized among laboratories. Here, we show that the microbiota's impact on fly triacylglyceride (TAG) levels-a commonly-measured metabolic index-depends on both preservatives and yeast, and combinatorial interactions among the three variables. In studies of conventional, axenic, and gnotobiotic flies, we found that microbial impacts were apparent only on specific yeast-by-preservative conditions, with TAG levels determined by a tripartite interaction of the three experimental factors. When comparing axenic and conventional flies, we found that preservatives caused more variance in host TAG than microbiota status, and certain yeast-preservative combinations even reversed effects of microbiota on TAG. Preservatives had major effects in axenic flies, suggesting either direct effects on the fly or indirect effects via media. However, Acetobacter pomorum buffers the fly against this effect, despite the preservatives inhibiting growth, indicating that this bacterium benefits the host in the face of mutual environmental toxicity. Our results suggest that antimicrobial preservatives have major impacts on host TAG, and that microbiota modulates host TAG dependent on the combination of the dietary factors of preservative formula and yeast batch. IMPORTANCE Drosophila melanogaster is a premier model for microbiome science, which has greatly enhanced our understanding of the basic biology of host-microbe interactions. However, often overlooked factors such as dietary composition, including yeast batch variability and preservative formula, may confound data interpretation of experiments within the same lab and lead to different findings when comparing between labs. Our study supports this notion; we find that the microbiota does not alter host TAG levels independently. Rather, TAG is modulated by combinatorial effects of microbiota, yeast batch, and preservative formula. Specific preservatives increase TAG even in germ-free flies, showing that a commonplace procedure in fly husbandry alters metabolic physiology. This work serves as a cautionary tale that fly rearing methodology can mask or drive microbiota-dependent metabolic changes and also cause microbiota-independent changes.

Protective effects of Acetobacter ghanensis against gliadin toxicity in intestinal epithelial cells with immunoregulatory and gluten-digestive properties.

PURPOSE: The aim of this study was to establish whether Acetobacter ghanensis, the probiotic characteristics of which were evaluated previously, attenuates gliadin-induced toxicity in intestinal epithelial cells with gluten-digestive and immunoregulatory properties. METHODS: A co-culture model of human intestinal epithelial cell (Caco-2) monolayers on top of peripheral blood mononuclear cells (PBMCs) obtained from patients with celiac disease (CD) was established. The gluten-digestive properties of A. ghanensis were determined by checking bacterial growth in a medium containing gluten as the main nitrogen source. The mRNA levels of genes encoding TJ-associated proteins were measured by quantitative real-time PCR (qRT-PCR). The concentrations of IL-6 and TNFα were determined by enzyme-linked immunosorbent assay (ELISA). RESULTS: We found that PT-gliadin disrupted intestinal barrier integrity by modulating the expression of TJ-associated genes encoding zonulin (increased by ~ 60%), zonula occludens-1 (ZO-1) (decreased by ~ 22%), and occludin (decreased by ~ 28%) in Caco-2 cells. Furthermore, PT-gliadin treatment in Caco-2 cells was associated with increased concentrations of IL-6 (~ 1.6-fold) and TNFα (~ twofold) from PBMCs. These modulatory effects of PT-gliadin, however, were suppressed when Caco-2 cells were subjected to A. ghanensis in the presence of PT-gliadin. As a factor underlying these protective effects, we showed that A. ghanensis could digest gluten peptides. CONCLUSIONS: To our knowledge, the current study is the first to demonstrate that A. ghanensis improves intestinal barrier functions by attenuating the modulatory effects of PT-gliadin with immunoregulatory and gluten-digestive properties.

Alcohol degradation, learning, and memory-enhancing effect of Acetobacter pasteurianus BP2201 in Caenorhabditis elegans model.

AIMS: This study aimed to investigate the probiotic effects of Acetobacter pasteurianus BP2201, isolated from brewing mass, for the treatment of alcohol-induced learning and memory ability impairments in a Caenorhabditis elegans model. METHODS AND RESULTS: Acetobacter pasteurianus BP2201 was examined for probiotic properties, including acid and bile salt resistance, ethanol degradation, antioxidant efficacy, hemolytic activity, and susceptibility to antibiotics. The strain displayed robust acid and bile salt tolerance, efficient ethanol degradation, potent antioxidant activity, and susceptibility to specific antibiotics. Additionally, in the C. elegans model, administering A. pasteurianus BP2201 significantly improved alcohol-induced learning and memory impairments. CONCLUSIONS: Acetobacter pasteurianus BP2201 proves to be a promising candidate strain for the treatment of learning and memory impairments induced by alcohol intake.

A bacteria-regulated gut peptide determines host dependence on specific bacteria to support host juvenile development and survival.

BACKGROUND: Commensal microorganisms have a significant impact on the physiology of host animals, including Drosophila. Lactobacillus and Acetobacter, the two most common commensal bacteria in Drosophila, stimulate fly development and growth, but the mechanisms underlying their functional interactions remain elusive. RESULTS: We found that imaginal morphogenesis protein-Late 2 (Imp-L2), a Drosophila homolog of insulin-like growth factor binding protein 7, is expressed in gut enterocytes in a bacteria-dependent manner, determining host dependence on specific bacteria for host development. Imp-L2 mutation abolished the stimulatory effects of Lactobacillus, but not of Acetobacter, on fly larval development. The lethality of the Imp-L2 mutant markedly increased under axenic conditions, which was reversed by Acetobacter, but not Lactobacillus, re-association. The host dependence on specific bacteria was determined by Imp-L2 expressed in enterocytes, which was repressed by Acetobacter, but not Lactobacillus. Mechanistically, Lactobacillus and Acetobacter differentially affected steroid hormone-mediated Imp-L2 expression and Imp-L2-specific FOXO regulation. CONCLUSIONS: Our finding may provide a way how host switches dependence between different bacterial species when benefiting from varying microbiota.

Acetobacter vaccinii sp. nov., a novel acetic acid bacterium isolated from blueberry fruit (Vaccinium corymbosum L.).

Strain C17-3T was isolated from blueberry fruits collected from a farmland located in Damyang-gun, Jeollanam-do, Republic of Korea. Phylogenetic analysis based on 16S rRNA gene sequences allocated strain C17-3T to the genus Acetobacter, where it occupied a rather isolated line of descent with Acetobacter ghanensis 430AT and Acetobacter lambici LMG 27439T as the nearest neighbours (98.9 % sequence similarity to both species). The highest average nucleotide identity and digital DNA-DNA hybridization values were 76.3 % and 21.7 % with Acetobacter garciniae TBRC 12339T; both values were well below the cutoff values for species delineation. Cells are strictly aerobic, Gram-stain-negative rods, catalase-positive and oxidase-negative. The DNA G+C content calculated from the genome sequence was 59.2 %. Major fatty acids were summed feature 8 (C18 : 1ω6c and/or C18 : 1ω7c) and C19 : 0cyclo ω8c. The major isoprenoid quinone was ubiquinone 9. On the basis of the results of phylogenetic analyses, phenotypic features and genomic comparisons, it is proposed that strain C17-3T represents a novel species of the genus Acetobacter and the name Acetobacter vaccinii sp. nov. is proposed. The type strain is C17-3T (= KACC 21233T = LMG 31758T).

Acetobacter senegalensis isolated from mango fruits: Its polyphasic characterization and adaptation to protect against stressors in the industrial production of vinegar: A review.

It has been more than a decade since Acetobacter senegalensis was isolated, identified and described as a thermotolerant strain of acetic acid bacteria. It was isolated from mango fruits in Senegal and used for industrial vinegar production in developing countries, mainly in sub-Saharan Africa. The strain was tested during several spirit vinegar fermentation processes at relatively high temperatures in accordance with African acclimation. The upstream fermentation process had significant stress factors, which are highlighted in this review so that the fermentation process can be better controlled. Due to its high industrial potential, this strain was extensively investigated by diverse industrial microbiologists worldwide; they concentrated on its microbiological, physiological and genomic features. A research group based in Belgium proposed an important project for the investigation of the whole-genome sequence of A. senegalensis. It would use a 454-pyrosequencing technique to determine and corroborate features that could give this strain significant diverse bio-industrial applications. For instance, its application in cocoa bean fermentation has made it a more suitable acetic acid bacterium for the making of chocolate than Acetobacter pasteurianus. Therefore, in this paper, we present a review that summarizes the current research on A. senegalensis at its microbial and genomic levels and also its specific bio-industrial applications, which can provide economic opportunities for African agribusiness. This review summarizes the physiological and genomic characteristics of Acetobacter senegalensis, a thermotolerant strain isolated from mango fruits and intended to be used in industrial vinegar fermentation processes. It also explores other bio-industrial applications such as cocoa fermentation. Vinegar fermentation is usually performed with mesophilic strains in temperate regions of the world. Developing countries, such as Senegal, import vinegar or make 'fake' vinegar by diluting acetic acid obtained from petrochemicals. The use of a thermotolerant Acetobacter senegalensis strain as a solid functional starter culture, as well as the design of a new adapted bioreactor, has significantly contributed to food security and the creation of small- to medium-sized enterprises that produce mango vinegar in West Africa.

Comparative pangenomic analyses and biotechnological potential of cocoa-related Acetobacter senegalensis strains.

Acetobacter senegalensis belongs to the group of acetic acid bacteria (AAB) that present potential biotechnological applications, for production of D-gluconate, cellulose and acetic acid. AAB can overcome heat and acid stresses by using strategies involving the overexpression of heat-shock proteins and enzymes from the complex pyrroquinoline-ADH, besides alcohol dehydrogenases (ADH). Nonetheless, the isolation of A. senegalensis and other AAB from food may be challenging due to presence of viable but non-culturable (VBNC) cells and due to uncertainties about nutritional requirements. To contribute for a better understanding of the ecology of AAB, this paper reports on the pangenome analysis of five strains of A. senegalensis recently isolated from a Brazilian spontaneous cocoa fermentation. The results showed biosynthetic clusters exclusively found in some cocoa-related AAB, such as those related to terpene pathways, which are important for flavour development. Genes related to oxidative stress were conserved in all the genomes, with multiple clusters. Moreover, there were genes coding for ADH and putative ABC transporters distributed in core, shell and cloud genomes, while chaperonin-encoding genes were present only in the core and soft-core genomes. Regarding quorum sensing, a response regulator gene was in the shell genome, and the gene encoding for acyl-homoserine lactone efflux protein was in the soft-core genome. There were quorum quenching-related genes, mainly encoding for lactonases, but also for acylases. Moreover, A. senegalensis did not have determinants of virulence or antibiotic resistance, which are good traits for strains intended to be applied in food fermentation.

Acetic acid acting as a signaling molecule in the quorum sensing system increases 2,3-butanediol production in Saccharomyces cerevisiae.

2,3-Butanediol (2,3-BD) has been extensively used in chemical syntheses. This study aimed to explore acetic acid as a signaling molecule that activates a quorum sensing (QS) system to promote the production of 2,3-BD. The yield of 2,3-BD is proportional to the cell density. Saccharomyces cerevisiae W141 does not produce 2,3-BD when the cell density is lower than the threshold concentration (OD600 nm = 10 or cell density 4.4 × 108 CFU/mL). When 1.5 g/L acetic acid is added, the yield of 2,3-BD is 3.01 ± 0.04 g/L. Subsequently, S. cerevisiae W141 was cocultured with Acetobacter pasteurianus Huniang 1.01 under the optimal conditions, the acetic acid production was increased by 76.7% and 30.6% compared with the original strain and the strain cultivated with 1.5 g/L acetic acid, and the yield of 2,3-BD was increased by 81.9% and 3.3%, respectively. This difference is due to the activity of acetyl lactic acid synthase (ILV2) and 2,3-BD dehydrogenase (BDH1), as the relative expression of the ilv2 and bdh1 genes is increased. The results showed that the biosynthesis of 2,3-BD was regulated by acetic acid as a signaling molecule. S. cerevisiae is a promising host for producing 2,3-BD for industrial applications.

The Peculiar Structure of Acetobacter pasteurianus CIP103108 LPS Core Oligosaccharide.

Acetobacter pasteurianus, a member of the Alphaproteobacteria, is an acetic acid-producing bacterium present on sugar-rich substrates such as such as fruits, flowers and vegetables and traditionally used in the production of fermented food. The preferred living habitat associated with acid conditions makes the structure of the bacterial cell wall interesting to study, due to expected uncommon features. We have used a combination of chemical, analytical and NMR spectroscopy approaches to define the complete structure of the core oligosaccharide from A. pasteurianus CIP103108 LPS. Interestingly, the core oligosaccharide displays a high concentration of negatively charged groups, structural features that might contribute to reinforcing the bacterial membrane.

Acetobacter garciniae sp. nov., an acetic acid bacterium isolated from fermented mangosteen peel in Thailand.

Two isolates, MS16-SU-2T and MS18-SU-3, obtained from fermented mangosteen peel in vinegar were suggested to constitute a new species assignable to the genus Acetobacter based on the results of 16S rRNA gene sequencing. The two isolates showed the highest sequence similarity (98.58%) to Acetobacter tropicalis NBRC 16470T and Acetobacter senegalensis LMG 23690T. However, the calculated similarity values were lower than the threshold for species demarcation. The phylogenetic analysis showed that the branches of the two isolates were separated from other Acetobacter species, and the two isolates constituted a new species in the genus Acetobacter. The genomic DNA of isolate MS16-SU-2T was sequenced. The assembled genome of the isolate was analysed, and the results showed that the highest average nucleotide identity value of 75.9 % was with Acetobacter papayae JCM 25143T and the highest digital DNA-DNA hybridization value of 25.1 % was with Acetobacter fallax LMG 1636T, which were lower than the cutoff values for species delineation. The phylogenetic tree based on the genome sequences showed that the lineage of isolate MS16-SU-2T was most closely related to A. papayae JCM 25143T and Acetobacter suratthaniensis TBRC 1719T, but separated from the branches of these two species. In addition, the two isolates could be distinguished from the type strains of closely related species by their phenotypic characteristics and MALDI-TOF profiles. Therefore, the two isolates, MS16-SU-2T (=TBRC 12339T=LMG 32243T) and MS18-SU-3 (=TBRC 12305), can be assigned to an independent species within the genus Acetobacter, and the name of Acetobacter garciniae sp. nov. is proposed for the two isolates.

Impacts of type II toxin-antitoxin systems on cell physiology and environmental behavior in acetic acid bacteria.

Acetic acid bacteria (AAB) are a group of Gram-negative and strictly aerobic microorganisms widely used in vinegar industry, especially the species belonging to the genera Acetobacter and Komagataeibacter. The environments inhabited by AAB during the vinegar fermentation, in particular those natural traditional bioprocesses, are complex and dynamically changed, usually accompanied by diverse microorganisms, bacteriophages, and the increasing acetic acid concentration. For this reason, how AAB survive to such harsh niches has always been an interesting research field. Previous omic analyses (e.g., genomics, proteomics, and transcriptomics) have provided abundant clues for the metabolic pathways and bioprocesses indispensable for the acid stress adaptation of AAB. Nevertheless, it is far from fully understanding what factors regulate these modular mechanisms overtly and covertly upon shifting environments. Bacterial toxin-antitoxin systems (TAS), usually consisting of a pair of genes encoding a stable toxin and an unstable antitoxin that is capable of counteracting the toxin, have been uncovered to have a variety of biological functions. Recent studies focusing on the role of TAS in Acetobacter pasteurianus suggest that TAS contribute substantially to the acid stress resistance. In this mini review, we discuss the biological functions of type II TAS in the context of AAB with regard to the acid stress resistance, persister formation and resuscitation, genome stability, and phage immunity. KEY POINTS: • Type II TAS act as regulators in the acid stress resistance of AAB. • Type II TAS are implicated in the formation of acid-tolerant persister cells in AAB. • Type II TAS are potential factors responsible for phage immunity and genome stability.

60Coγ induction improves the protective effect of Acetobacter pasteurianus against ionizing radiation in mice.

Exposure to ionizing radiation (IR) tends to cause serious health concerns. Thus, radioprotective agents are vital for the population exposed to radiation. As microorganisms have the advantages of fast reproduction and no geographical restrictions, direct microbe-based and environmental induction compounds are thriving radioprotectants resources. Oxidative system and oxidase in Acetobacter pasteurianus are unique and intriguing, the radioprotective effect of the cell-free extract from A. pasteurianus (APE) and 60Coγ-treated extract (IRE) were comparatively investigated in the present study. The survival rate of A. pasteurianus with IRE addition was 149.1% in H2O2 damage test, while that with APE was only 10.4%. The viability of 60Coγ-treated AML-12 cells was increased by 18.8% with IRE addition, yet APE showed no significant radioprotective effect. Moreover, in 60Coγ-treated mice, IRE could significantly protect the white blood cell, improve the liver index, and attenuate the injuries of immune organs in mice. Administration of IRE significantly raised the activities of superoxide dismutase (SOD) and reduced the products of lipid peroxidation. These results clarified that gavage with APE and IRE presented notable antioxidant and radioprotective efficacy. A. pasteurianus showed appealing potential to be novel radioprotective bioagents and 60Coγ treatment on microbe could be a new method for the development of better radioprotectant. KEY POINTS: • 60Coγ induction could improve the radioprotective effect of APE. • IRE protected white blood cell in mice under IR. • IRE products have broad application prospects in radioprotection based on microbes.

Toxin-antitoxin HicAB regulates the formation of persister cells responsible for the acid stress resistance in Acetobacter pasteurianus.

Elucidation of the acetic acid resistance (AAR) mechanisms is of great significance to the development of industrial microbial species, specifically to the acetic acid bacteria (AAB) in vinegar industry. Currently, the role of population heterogeneity in the AAR of AAB is still unclear. In this study, we investigated the persister formation in AAB and the physiological role of HicAB in Acetobacter pasteurianus Ab3. We found that AAB were able to produce a high level of persister cells (10-2 to 100 in frequency) in the exponential-phase cultures. Initial addition of acetic acid and ethanol reduced the ratio of persister cells in A. pasteurianus by promoting the intracellular ATP level. Further, we demonstrated that HicAB was an important regulator of AAR in A. pasteurianus Ab3. Strains lacking hicAB showed a decreased survival under acetic acid exposure. Deletion of hicAB significantly diminished the acetic acid production, acetification rate, and persister formation in A. pasteurianus Ab3, underscoring the correlation between hicAB, persister formation, and acid stress resistance. By transcriptomic analysis (RNA-seq), we revealed that HicAB contributed to the survival of A. pasteurianus Ab3 under high acid stress by upregulating the expression of genes involved in the acetic acid over-oxidation and transport, 2-methylcitrate cycle, and oxidative phosphorylation. Collectively, the results of this study refresh our current understanding of the AAR mechanisms in A. pasteurianus, which may facilitate the development of novel ways for improving its industrial performance and direct the scaled-up vinegar production. KEY POINTS: • AAB strains form persister cells with different frequencies. • A. pasteurianus are able to form acid-tolerant persister cells. • HicAB contributes to the AAR and persister formation in A. pasteurianus Ab3.