AIMS:Fructobacillus requires electron acceptors (fructose, pyruvate, or oxygen) for glucose metabolism. They metabolize fructose as an energy source by using fructokinase (FK) and glucose-6-phosphate isomerase (GPI), and as an electron acceptor, reducing it to the low-calorie sugar mannitol by using mannitol 2-dehydrogenase (MDH) enzyme. We aimed to study the physiological and biochemical traits of Fructobacillus sp. CRL 2054 and F. tropaeoli CRL 2034, belonging to two different genomic clades, to further improve their mannitol production. METHODS AND RESULTS:Microbial growth and mannitol production under different carbon sources, saccharide concentrations, and electron acceptors were assayed. The activities and gene expression of the enzymes involved in carbohydrate metabolism and mannitol production by Fructobacillus, along with their genomic context, were determined. Both strains grew up to 40% (w v-1) carbohydrates, while mannitol production decreased with 20% (w v-1) of sugars. Pyruvate competed with fructose as an electron acceptor, reducing mannitol production and MDH activity in both strains. The mdh gene was upregulated while fk and gpi genes were downregulated under glucose, regulating the use of fructose as electron acceptor. CONCLUSIONS:Both Fructobacillus strains were highly osmotolerant. Mannitol production decreased with sugar concentrations above 15% (w v-1), suggesting its use as a compatible solute against osmotic stress. Pyruvate competed with fructose as an electron acceptor, reducing mannitol production, while fructose was reduced to mannitol in the presence of glucose by regulating genes involved in fructose metabolism.

We report here a draft genome assembly of Lacticaseibacillus rhamnosus CRL 2244, recovered from wastewater in Argentina. The genome has a size of 2,898,100 bp, with G + C content of 46.73%. Comparative analysis reveals that its closest relative is L. rhamnosus 1.0320 (GCF_006151905.1), with an average nucleotide identity of 97.46%.

A growing increase in the number of serious infections caused by multidrug resistant bacteria (MDR) is challenging our society. Despite efforts to discover novel therapeutic options, few antibiotics targeting MDR have been approved by the Food and Drug Administration (FDA). Lactic acid bacteria have emerged as a promising therapeutic alternative due to their demonstrated ability to combat MDR pathogens in vitro. Our previous co-culture studies showed Lacticaseibacillus rhamnosus CRL 2244 as having a potent killing effect against carbapenem-resistant Acinetobacter baumannii (CRAB) strains. Here we report that cell-free conditioned media (CFCM) samples obtained from Lcb. rhamnosus CRL 2244 cultures incubated at different times display antimicrobial activity against 43 different pathogens, including CRAB, methicillin-resistant Staphylococcus aureus (MRSA) and carbapenemase Klebsiella pneumoniae (KPC)-positive strains. Furthermore, transwell and ultrafiltration analyses together with physical and chemical/biochemical tests showed that Lcb. rhamnosus CRL 2244 secretes a <3 kDa metabolite(s) whose antimicrobial activity is not significantly impaired by mild changes in pH, temperature and various enzymatic treatments. Furthermore, sensitivity and time-kill assays showed that the bactericidal activity of the Lcb. rhamnosus CRL 2244 metabolite(s) enhances the activity of some current FDA approved antibiotics. We hypothesize that this observation could be due to the effects of Lcb. rhamnosus CRL 2244 metabolite(s) on cell morphology and the enhanced transcriptional expression of genes coding for the phenylacetate (PAA) and histidine catabolic Hut pathways, metal acquisition and biofilm formation, all of which are associated with bacterial virulence. Interestingly, the extracellular presence of Lcb. rhamnosus CRL 2244 induced the transcription of the gene coding for the CidA/LgrA protein, which is involved in programmed cell death in some bacteria. Overall, the findings presented in this report underscore the promising potential of the compound(s) released by Lcb. rhamnosus CRL2244 as an alternative and/or complementary option to treat infections caused by A. baumannii as well as other MDR bacterial pathogens.

Yeast contamination is an important problem that affects wine production worldwide. In the present work, fermentative and biocontrol properties under winemaking conditions of the two killer strains, Saccharomyces cerevisiae Cf8 and Wickerhamomyces anomalus Cf20, were evaluated. S. cerevisiae Cf8 and its combination with W. anomalus Cf20 were able to effectively control the growth of Meyerozyma guilliermondii Cd6 at low SO2 concentrations during Malbec must fermentation. Although the killer strain Cf8 alone exerted lower inhibitory activity, it modulated the growth of the strain Cd6, which positively influenced on wine aroma and complexity without being detrimental to product quality. Malbec wine produced by mixed culture Cf8 and Cd6 was the preferred one by the judges in the sensory analysis. To our knowledge, this is the first study made on red wines produced with indigenous killer yeasts from the Northwest Region of Argentina, as well as the first report of the modulation of potential spoilage yeasts into positive starters using killer yeasts in wine production. These results suggest that killer yeasts could be utilized as starter cultures to produce regional wines using low concentrations of SO2.

Mannitol is a natural polyol used in the food, medical and pharmaceutical industries. In this work, a simplified low-cost culture medium using fructose syrup as a carbon source was formulated for mannitol production by Fructobacillus sp. CRL 2054 and F. tropaeoli CRL 2034. To this end, the effect of different medium components in bacterial growth and mannitol synthesis was assessed by applying the Plackett-Burman statistical design. The formulated FSYP-min was used for fermentations at constant pH of 5.0 in a 2 L bioreactor, where two concentrations of fructose syrup (10 and 20 %, w/v, of total sugars) were evaluated. High mannitol concentrations (ca. 90 g/L) and volumetric productivities (3.7 g/L*h) were achieved by both strains using 20 % (w/v) of sugars; these mannitol values are one of the highest reported for LAB to date. Finally, high -purity mannitol crystals were successfully extracted after fermentation with the formulated culture medium.

Abstract Background Acinetobacter baumannii (AB) is a recognized nosocomial pathogen of critical importance Most circulating AB strains are carbapenem-resistant (CRAB), which severely complicates therapeutics with available antibiotics. Probiotic lactic acid bacteria constitute a promising therapeutic alternative. Previously, we determined that Lacticaseibacillus rhamnosus R3 (LR-R3) exerts a strong inhibitory capacity on the model strain A118 (susceptible to antibiotics). In this analysis, the antimicrobial activity of LR-R3 against type CRAB hypervirulent strain AB5075 was evaluated. Figure 1 A) Transwell migration assay. AB5075 viability after 24h exposure to LR-R3 CFCM. B) CFCM activity obtained from 96h culture of LR-R3 on CRAB strains. Methods The inhibitory activity of cell pellet and its cell-free supernatants (CFCM) were determined, respectively, by the soft-agar overlay method, CFCM activity, and transwell migration assay. Also, killing assays and scanning microscopy imaging were performed under co-culture conditions. Lastly, AB5075 transcriptional response when exposed to LR-R3 was assessed by RT-qPCR. Results The lactic acid bacteria LR-R3 demonstrated a strong inhibitory capacity on AB5075 strain (inhibition halo diameter, DHI >20 mm), with loss of cell viability at 4h of co-culture conditions. The CFCM of LR-R3 also showed similar antimicrobial activity on AB5075 (Fig 1A) and against others CRAB strains (Fig 1B), suggesting that the inhibitory effect observed is due to the presence of a compound or metabolite produced and secreted by the lactobacillus. Microscopy images showed increase formation of outer membrane vesicles (OMVs) and the presence of nanotubes. In addition, significant changes in the expression levels of the studied genes were observed in AB5075 in co-culture with LR-R3: increase in the expression of genes involved in biofilm (csuAB, csuB, ompA); and decrease in the expression of genes involved in the synthesis and utilization of iron (bauA, exbD, bfnA, basE, pirA), and genes related to fatty acid and lipid metabolism (paaA, paaB). Conclusion The results obtained allowed the identification of Lcb. rhamnosus R3 as a probiotic strain with antagonistic activity on the nosocomial pathogen A. baumannii. In addition, it was shown that LR-R3 alters iron and fatty acid metabolism, by virtue of this interaction. This work constitutes the basis for future studies necessary to elucidate the mechanism involved. Disclosures Robert A. bonomo, MD, Entasis, Merck, VenatoRx, Wockhardt: Grant/Research Support

During meat processing, lactic acid bacteria (LAB) have to competitively adapt to the hostile environment produced by curing additives (CA). The objective of this study was to investigate the ability of Latilactobacillus curvatus CRL 705, a bioprotective strain of meat origin, to adapt to CA. A physiological and proteomic approach was performed. CRL 705 was grown in a chemically defined medium (CDM) containing specific concentrations of CA (NaCl, nitrite, sucrose, and ascorbic acid). The results showed minor differences in growth kinetics in the presence of CA. Glucose consumption, present in the CDM, and production of lactic acid and bacteriocins were not significantly affected. Proteomic analyses indicated that most of the identified proteins (36 out of 39) mainly related to carbohydrate metabolism (18%), posttranslational modifications (15.6%), energy production and conversion (11.1%), translation (11.1%), and nucleotide metabolism (8.9%) were underexpressed. In response to the studied CA, CRL 705 slowed down its general metabolism, achieving slight changes in physiological and proteomic parameters. The observed performance is another characteristic that extends the well-known competitive profile of CRL 705 as a meat starter and bioprotective culture. This is the first report dealing with the impact of CA on LAB proteomics.

Mannitol is a natural polyol extensively used in the food, medical and pharmaceutical industries. In this work, a simplified low-cost culture medium using fructose syrup as a carbon source was formulated for mannitol production by Fructobacillus sp. CRL 2054 and F. tropaeoli CRL 2034. To this end, the effect of different medium components in bacterial growth and mannitol synthesis was assessed by applying the Plackett-Burman statistical design. The formulated FSYP-min was used for fermentations at constant pH of 5.0 in a 2 L bioreactor, where two concentrations of fructose syrup (10 and 20%, w/v, of total sugars) were evaluated. High mannitol concentrations (ca. 90 g/L) were achieved by both strains under 20% (w/v) of sugars. Finally, high-purity mannitol crystals were successfully isolated after fermentation with the formulated low-cost culture medium.

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a recognized nosocomial pathogen with limited antibiotic treatment options. Lactic acid bacteria (LAB) constitute a promising therapeutic alternative. Here we studied the antibacterial properties of a collection of LAB strains using phenotypic and transcriptomic analysis against A. baumannii clinical strains. One strain, Lacticaseibacillus rhamnosus CRL 2244, demonstrated a potent inhibitory capacity on A. baumannii with a significant killing activity. Scanning electron microscopy images showed changes in the morphology of A. baumannii with an increased formation of outer membrane vesicles. Significant changes in the expression levels of a wide variety of genes were also observed. Interestingly, most of the modified genes were involved in a metabolic pathway known to be associated with the survival of A. baumannii . The paa operon, Hut system, and fatty acid degradation were some of the pathways that were induced. The analysis reveals the impact of Lcb. rhamnosus CRL 2244 on A. baumannii response, resulting in bacterial stress and subsequent cell death. These findings highlight the antibacterial properties of Lcb. rhamnosus CRL 2244 and its potential as an alternative or complementary strategy for treating infections. Further exploration and development of LAB as a treatment option could provide valuable alternatives for combating CRAB infections.

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a recognized nosocomial pathogen with limited antibiotic treatment options. Lactic acid bacteria (LAB) constitute a promising therapeutic alternative. Here we studied the antibacterial properties of a collection of LAB strains using phenotypic and transcriptomic analysis against A. baumannii clinical strains. One strain, Lacticaseibacillus rhamnosus CRL 2244, demonstrated a potent inhibitory capacity on A. baumannii with a significant killing activity. Scanning electron microscopy images showed changes in the morphology of A. baumannii with an increased formation of outer membrane vesicles. Significant changes in the expression levels of a wide variety of genes were also observed. Interestingly, most of the modified genes were involved in a metabolic pathway known to be associated with the survival of A. baumannii. The paa operon, Hut system, and fatty acid degradation were some of the pathways that were induced. The analysis reveals the impact of Lcb. rhamnosus CRL 2244 on A. baumannii response, resulting in bacterial stress and subsequent cell death. These findings highlight the antibacterial properties of Lcb. rhamnosus CRL 2244 and its potential as an alternative or complementary strategy for treating infections. Further exploration and development of LAB as a treatment option could provide valuable alternatives for combating CRAB infections.

The Fructobacillus genus is a group of obligately fructophilic lactic acid bacteria (FLAB) that requires the use of fructose or another electron acceptor for their growth. In this work, we performed a comparative genomic analysis within the genus Fructobacillus by using 24 available genomes to evaluate genomic and metabolic differences among these organisms. In the genome of these strains, which varies between 1.15- and 1.75-Mbp, nineteen intact prophage regions, and seven complete CRISPR-Cas type II systems were found. Phylogenetic analyses located the studied genomes in two different clades. A pangenome analysis and a functional classification of their genes revealed that genomes of the first clade presented fewer genes involved in the synthesis of amino acids and other nitrogen compounds. Moreover, the presence of genes strictly related to the use of fructose and electron acceptors was variable within the genus, although these variations were not always related to the phylogeny.

Between 2015 and 2019, we hosted an International Phage Course at Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina. The 2-week full-time course was hands-on and included lectures from renowned phage biologists. Participating students were able to meet and discuss with recognized experts from around the world in a familiar setting, facilitating the establishment of scientific collaborations and the expansion of their networks. Eighty-four students from 14 Latin American countries have participated in the course, which included isolation, characterization, genome sequencing, and annotation of novel phages. We have successfully created a coursework that enabled the acquisition of new knowledge and expertise in bacteriophage biology and strengthened ties among Latin American colleagues.

Here, we report the genome sequence of a Siphoviridae phage named vB_SauS_BaqSau1 (BaqSau1), infecting Staphylococcus aureus. Phage BaqSau1 was isolated from a sewage water treatment plant in Sahagún, Córdoba, Colombia. It has a double-stranded DNA (dsDNA) genome of 44,384 bp with 67 predicted genes, including a lysin containing a CHAP (cysteine, histidine-dependent amidohydrolase/peptidase) domain.

Volume 9, no. 15, e00147-20, 2020, [https://doi.org/10.1128/MRA.00147-20][1]. Page 1: The author affiliations should appear as shown in this correction. [1]: /lookup/doi/10.1128/MRA.00147-20

The nucleotide sequences of plasmids pRC12 (12,342 bp; GC 43.99%) and pRC18 (18,664 bp; GC 34.33%), harbored by the bacteriocin-producer Lactobacillus curvatus CRL 705, were determined and analyzed. Plasmids pRC12 and pRC18 share a region with high DNA identity (> 83% identity between RepA, a Type II toxin-antitoxin system and a tyrosine integrase genes) and are stably maintained in their natural host L. curvatus CRL 705. Both plasmids are low copy number and belong to the theta-type replicating group. While pRC12 is a pUCL287-like plasmid that possesses iterons and the repA and repB genes for replication, pRC18 harbors a 168 amino acid replication protein affiliated to RepB, which was named RepB'. Plasmid pRC18 also possesses a pUCL287-like repA gene but it was disrupted by an 11 kb insertion element that contains RepB', several transposases/IS elements, and the lactocin Lac705 operon. An Escherichia coli / Lactobacillus shuttle vector, named plasmid p3B1, carrying the pRC18 replicon (i.e. repB' and replication origin), a chloramphenicol resistance gene and a pBluescript backbone, was constructed and used to define the host range of RepB'. Chloramphenicol-resistant transformants were obtained after electroporation of Lactobacillus plantarum CRL 691, Lactobacillus sakei 23K and a plasmid-cured derivative of L. curvatus CRL 705, but not of L. curvatus DSM 20019 or Lactococcus lactis NZ9000. Depending on the host, transformation efficiency ranged from 102 to 107 per μg of DNA; in the new hosts, the plasmid was relatively stable as 29-53% of recombinants kept it after cell growth for 100 generations in the absence of selective pressure. Plasmid p3B1 could therefore be used for cloning and functional studies in several Lactobacillus species.

The enzymes D- and L-lactate dehydrogenase are involved in the reduction of pyruvate to D(+)- and L(−)-lactate, respectively. The fig-origin strain Fructobacillus tropaeoli CRL 2034 produces D- and L-lactic acids in a 9:1 ratio. In this work, two D-ldh (ldh1 and ldh2) and one L-ldh (ldh3) genes were found in the CRL 2034 genome. ldh1 and ldh2 are homologous (79% identity) and organized as contiguous operons, each gene containing 996 base pair (bp) and encoding for a 331-amino acid (aa) protein (74% identity). In contrast, ldh3 is a 927-bp gene coding for a 308-aa protein. The identity between ldh1/ldh2 and ldh3 was lower than 48%. To elucidate the role of these genes in the synthesis of lactic acid by the Fructobacillus strain, plasmid insertion mutants in each gene were generated and characterized. The growth kinetic parameters were affected only in CRL2034 ldh1::pRV300 cells, this mutant showing the lowest total lactic acid production (4.50 ± 0.15 versus 6.36 ± 0.67 g/L of wild-type strain), with a D/L ratio of 7.1:2.9. These results showed that the ldh1 gene is primarily responsible for lactic acid production by the studied strain. A comparative analysis among strains of the five Fructobacillus species revealed that the identity of D-LDH proteins was higher than 70%, while the identity of L-LDH was over 60%. Finally, phylogenetic analysis of D- and L-LDHs revealed that only D-LDH phylogeny was consistent to the phylogenetic evolution among Fructobacillus and evolutionarily related genera.

Introduction: Because of the clinical relevance of Mycobacteria, and from a therapeutic perspective, there is an increasing interest to study phages that infect bacteria belonging to this genus. Materials and Methods: A phage was isolated from a soil sample, using Mycobacterium smegmatis as host. Its characterization included sequencing, annotation, and analysis of the genome, host range determination, and electron microscopy imaging. Results: Mycobacterium phage vB_MsmS_Celfi is a temperate phage able to infect Mycobacterium tuberculosis with high efficiency. From electron microscopy images, Celfi belongs to the Siphoviridae family. Genome analysis classified phage Celfi into cluster L, subcluster L2 of Actinobacteriophage clusters. Mycobacterium phage Celfi exhibits a Lysin B distant to those present in other members of the subcluster and other mycobacteriophages. Conclusions: The discovery of new phages that infect M. tuberculosis could contribute to the development of novel tools for detection systems and future treatment of the disease.

We report the draft genome sequence of Fructobacillus tropaeoli CRL 2034, a strain isolated from ripe fig in Tucumán province, Argentina. The interest in studying the genome of this fructophilic lactic acid bacterium strain was motivated by its ability to produce high levels of mannitol from fructose. This polyol has multiple industrial applications; however, it is mainly used as low calorie sugar in the food industry. The assembled genome of this strain consists of a 1.66-Mbp circular chromosome with 1465 coding sequences and a G+C content of 44.6%. The analysis of this genome supports the one step reaction of fructose reduction to mannitol by the mannitol 2-dehydrogenase enzyme, which together with a fructose permease, were identified as involved in mannitol synthesis. In addition, a phylogenetic analysis was performed including other Leuconostocaceae members to which the Fructobacillus genus belongs to; according to the 16S rRNA gene sequences, the strain CRL 2034 was located in the Fructobacillus clade. The present genome sequence could be useful to further elucidate regulatory processes of mannitol and other bioactive metabolites and to highlight the biotechnological potential of this fruit-origin Fructobacillus strain.