Lactic Acid Resistance Research Articles

INFLUÊNCIA DO EXERCÍCIO DE ALTA INTENSIDADE SOBRE A APTIDÃO FÍSICA DOS NADADORES

ABSTRACT Introduction High-intensity swimming requires athletes to have explosive power, endurance, lactic acid resistance, aerobic metabolism, and other qualities. Pre-competition physical training is mainly based on high interval training, promoting ATP-CP synthesis in the body. It can enhance the resistance to lactic acid and promote lactic acid clearance. Objective This article explores the effect of high-intensity pre-competition training on the physical fitness of swimmers. The results can be used as a reference for swimmers to perform high-intensity training before the competition. Methods Eight swimmers were selected by random sampling. The study subjects received eight weeks of high-intensity training before the competition. The athletes’ gas metabolism and anaerobic thresholds were detected before and after training. At the same time, the physiological and chemical indicators of the experimental subjects were detected in this paper. Finally, this paper analyzes the experimental results by employing mathematical statistics. Results The metabolism function of the athletes changed significantly in the later period of pre-competition training (P<0.05). Serum lactate concentration had no significant effect on the anaerobic threshold (P>0.05). Conclusion High-intensity exercise has a particular promotion effect on improving the physical quality of swimmers. This exercise can lay a solid foundation for the swimmer’s physical fitness. Level of evidence II; Therapeutic studies – investigation of treatment results.

New Insights into the Lactic Acid Resistance Determinants of Listeria monocytogenes Based on Transposon Sequencing and Transcriptome Sequencing Analyses.

Listeria monocytogenes is a foodborne pathogen that can tolerate a variety of extreme environments. In particular, its acid resistance (AR) capability is considered one of the key factors threating food safety. Here, we employed a microbial functional genomic technology termed transposon sequencing (Tn-seq), leading to the identification of two genes involved in cell wall peptidoglycan biosynthesis (murF) and phosphate transport (lmo2248) that play key roles in lactic acid resistance (LAR) of L. monocytogenes. Deletion of lmo2248 significantly impaired the ability of LAR in L. monocytogenes, demonstrating the accuracy of the Tn-seq results. Transcriptome analysis revealed that 31.7% of the L. monocytogenes genes on the genome were differentially expressed under lactic acid (LA) treatment, in which genes involved in phosphate transport were influenced most significantly. These findings shed light on the LAR mechanisms of L. monocytogenes, which may contribute to the development of novel strategies against foodborne pathogens. IMPORTANCE Listeria monocytogenes is a Gram-positive foodborne pathogen with high lethality and strong stress resistance, and its strong acid tolerance leads to many foodborne illnesses occurring in low-pH foods. Lactic acid is a generally recognized as safe (GRAS) food additive approved for use by the FDA. However, the genetic determinants of lactic acid resistance in L. monocytogenes have not been fully identified. In this study, the lactic acid resistance determinants of L. monocytogenes were comprehensively identified by Tn-seq on a genome-wide scale. Two genes, murF (cell wall peptidoglycan biosynthesis) and lmo2248 (phosphate transport), were identified to play an important role in the lactic acid resistance. Moreover, genome-wide transcriptomic analysis showed that phosphotransferase system (PTS)-related genes play a key role at the transcriptional level. These findings contribute to a better understanding of the lactic acid resistance mechanism of L. monocytogenes and may provide unique targets for the development of other novel antimicrobial agents.

Lactic Acid Resistance and Population Structure of Escherichia coli from Meat Processing Environment.

ABSTRACTTo explore the effect of beef processing on Escherichia coli populations in relation to lactic acid resistance, this study investigated the links among acid response, phylogenetic structure, genome diversity, and genotypes associated with acid resistance of meat plant E. coli. Generic E. coli isolates (n = 700) were from carcasses, fabrication equipment, and beef products. Acid treatment was carried out in Luria-Bertani broth containing 5.5% lactic acid (pH 2.9). Log reductions of E. coli ranged from <0.5 to >5 log CFU/mL (median: 1.37 log). No difference in lactic acid resistance was observed between E. coli populations recovered before and after a processing step or antimicrobial interventions. E. coli from the preintervention carcasses were slightly more resistant than E. coli isolated from equipment, differing by <0.5 log unit. Acid-resistant E. coli (log reduction <1, n = 45) had a higher prevalence of genes related to energy metabolism (ydj, xap, ato) and oxidative stress (fec, ymjC) than the less resistant E. coli (log reduction >1, n = 133). The ydj and ato operons were abundant in E. coli from preintervention carcasses. In contrast, fec genes were abundant in E. coli from equipment surfaces. The preintervention E. coli contained phylogroups A and B1 in relatively equal proportions. Phylogroup B1 predominated (95%) in the population from equipment. Of note, E. coli collected after sanitation shared either the antigens of O8 or H21. Additionally, genome diversity decreased after chilling and equipment sanitation. Overall, beef processing did not select for E. coli resistant to lactic acid but shaped the population structure.IMPORTANCE Antimicrobial interventions have significantly reduced the microbial loads on carcasses/meat products; however, the wide use of chemical and physical biocides has raised concerns over their potential for selecting resistant populations in the beef processing environment. Phenotyping of acid resistance and whole-genome analysis described in this study demonstrated beef processing practices led to differences in acid resistance, genotype, and population structure between carcass- and equipment-associated E. coli but did not select for the acid-resistant population. Results indicate that genes coding for the metabolism of long-chain sugar acids (ydj) and short-chain fatty acids (ato) were more prevalent in carcass-associated than equipment-associated E. coli. These results suggest E. coli from carcasses and equipment surfaces have been exposed to different selective pressures. The findings improve our understanding of the microbial ecology of E. coli in food processing environments and in general.

Identification and Investigation of properties of strains Enterococcus spp. Isolated from artisanal Carpathian cheese

Natural fermented dairy products are a source of new promising strains of lactic acid bacteria (LAB). The purpose of the study was to find new strains of LAB isolated from traditional dairy products, useful for industrial applications as a component of a starter. 25 cultures out of 106 microbial cultures isolated from artisanal Carpathian cheeses made from raw ewe's milk in Ukraine belong to the Enterococcus genera. Four (SB6, SB12, SB18 and SB20) strains were not registered in the National Center for Biotechnology Information database, we registered them in the database as E. faecium under numbers MZ227257, MZ227255, MZ227254, MZ227256 respectively. These strains have shown moderate lactic acid production ability (pH 4.99–5.10) and resistance to 6.5% salt concentration. Despite the fact that by the nucleotide sequence of 16 S rRNA strains of enterococci belonged to the same species of E. faecium, they differed slightly in biochemical properties. All strains showed moderate antagonistic activity against E. coli, S. enteritidis, E. aerogenes, P. mirabilis and P. aeruginosa, but did not show antagonistic activity against S. aureus. Strains showed sensitivity to antibiotics, with the exception of aminoglycosides; they did not exhibit pathogenic properties and can be used for food production.

Extracorporeal membrane oxygenation for acute respiratory distress syndrome caused by acute phosgene poisoning: a report of 4 cases

To evaluate the protective effect and curative effect of early treatment with extracorporeal membrane oxygenation (ECMO) in severe patients with acute respiratory distress syndrome (ARDS) caused by acute phosgene poisoning. The course of treatment of 4 cases of ARDS caused by acute phosgene poisoning admitted to intensive care unit (ICU) of Jiangxi Provincial People's Hospital in April 2018 was retrospectively analyzed. The treatment parameters in patients before and after the ECMO treatment at 1, 3, 7 days were collected, including pH of the arterial blood, arterial partial pressure of carbon dioxide (PaCO2), arterial partial pressure of oxygen (PaO2), blood lactic acid (Lac) and systemic vascular resistance index (SVRI), cardiac index (CI), extravascular lung water index (ELWI), plateau pressure (Pplat), positive end-expiratory pressure (PEEP), driving pressure (ΔP), and acute physiology and chronic health evaluation II (APACHE II), the length of ICU stay, the treatment duration of ECMO and the duration of mechanical ventilation. After admitted in hospital, the 4 patients were all put on tracheal intubation and ventilator, but the ventilator support conditions were high, the oxygenation and internal environment were unstable. Therefore, ECMO therapy was performed on the next day after admission. Oxygenation was improved obviously after treatment, ventilator support conditions could be obviously reduced, including 3-6 mL/kg of the small tidal volume, 8-10 cmH2O (1 cmH2O = 0.098 kPa) of the PEEP, 0.30 of the inhaled oxygen concentration (FiO2), and other lung protection rest strategies. The parameters were improved obviously after the ECMO treatment compared with before, from the 1st day after the ECMO treatment, PaO2, SVRI rose obviously, Lac, ELWI, Pplat, PEEP, ΔP, APACHE II were significantly decreased [PaO2 (mmHg, 1 mmHg = 0.133 kPa): 85.5±10.7 vs. 54.2±4.5, SVRI (kPa×s×L-1×m-2): 153.6±9.4 vs. 118.0±12.6, Lac (mmol/L): 2.15±0.19 vs. 4.93±0.96, ELWI (mL/kg): 17.73±2.99 vs. 20.45±4.13, Pplat (cmH2O): 19.25±2.21 vs. 35.75±2.22, PEEP (cmH2O): 9.0±1.2 vs. 13.5±1.7, ΔP (cmH2O): 10.25±1.26 vs. 22.25±3.86, APACHE II: 17.25±2.22 vs. 26.50±2.08, all P < 0.05]; pH and CI were significantly increased after 3 days treatment, and PaCO2 was significantly decreased [pH: 7.43±0.05 vs. 7.21±0.13, CI (mL×s-1×m-2): 64.35±3.17 vs. 59.51±3.17, PaCO2 (mmHg): 42.0±2.2 vs. 55.0±8.5, all P < 0.05]. All the 4 patients were treated successfully and discharged after improvement. The length of ICU stay was 8-27 days, with an average (13.5±9.0) days; the treatment duration of ECMO was 6-12 days, with an average (8.0±2.7) days; the duration of mechanical ventilation was 6-20 days, with an average (10.75±6.19) days. Early treatment with ECMO can significantly improve the oxygenation of severe ARDS caused by acute phosgene poisoning, eliminate excessive CO2 in the body, reduce ventilator-associated lung injury, and improve the prognosis.

Transient MutS-Based Hypermutation System for Adaptive Evolution of Lactobacillus casei to Low pH.

This study explored transient inactivation of the gene encoding the DNA mismatch repair enzyme MutS as a tool for adaptive evolution of Lactobacillus casei MutS deletion derivatives of L. casei 12A and ATCC 334 were constructed and subjected to a 100-day adaptive evolution process to increase lactic acid resistance at low pH. Wild-type parental strains were also subjected to this treatment. At the end of the process, the ΔmutS lesion was repaired in representative L. casei 12A and ATCC 334 ΔmutS mutant isolates. Growth studies in broth at pH 4.0 (titrated with lactic acid) showed that all four adapted strains grew more rapidly, to higher cell densities, and produced significantly more lactic acid than untreated wild-type cells. However, the adapted ΔmutS derivative mutants showed the greatest increases in growth and lactic acid production. Further characterization of the L. casei 12A-adapted ΔmutS derivative revealed that it had a significantly smaller cell volume, a rougher cell surface, and significantly better survival at pH 2.5 than parental L. casei 12A. Genome sequence analysis confirmed that transient mutS inactivation decreased DNA replication fidelity in both L. casei strains, and it identified genetic changes that might contribute to the lactic acid-resistant phenotypes of adapted cells. Targeted inactivation of three genes that had acquired nonsense mutations in the adapted L. casei 12A ΔmutS mutant derivative showed that NADH dehydrogenase (ndh), phosphate transport ATP-binding protein PstB (pstB), and two-component signal transduction system (TCS) quorum-sensing histidine protein kinase (hpk) genes act in combination to increase lactic acid resistance in L. casei 12A.IMPORTANCE Adaptive evolution has been applied to microorganisms to increase industrially desirable phenotypes, including acid resistance. We developed a method to increase the adaptability of Lactobacillus casei 12A and ATCC 334 through transient inactivation of the DNA mismatch repair enzyme MutS. Here, we show this method was effective in increasing the resistance of L. casei to lactic acid at low pH. Additionally, we identified three genes that contribute to increased acid resistance in L. casei 12A. These results provide valuable insight on methods to enhance an organism's fitness to complex phenotypes through adaptive evolution and targeted gene inactivation.

Overexpression of ESBP6 improves lactic acid resistance and production in Saccharomyces cerevisiae

Polylactic acid plastics are receiving increasing attention for the control of atmospheric CO2 emissions. Lactic acid, the building block for polylactic acid, is produced by fermentation technology from renewable carbon sources. The yeast Saccharomyces cerevisiae, harboring the lactate dehydrogenases gene (LDH), produces lactic acid at a large scale due to its strong acid resistance, to its simple nutritional requirements and to its ease of genetic engineering. Since improvement of lactic acid resistance is correlated with an increase of lactic acid production under non-neutralizing condition, we isolated a novel gene that enhances lactic acid resistance using a multi-copy yeast genomic DNA library. In this study, we identified the ESBP6 gene, which increases lactic acid resistance when overexpressed and which encodes a protein with similarity to monocarboxylate permeases. Although ESBP6 was not induced in response to lactic acid stress, it caused weak but reproducible sensitivity to lactic acid when disrupted. Furthermore, intracellular pH in the ESBP6 overexpressing strain was higher than that in the wild-type strain under lactic acid stressed condition, suggesting that Esbp6 plays some roles in lactic acid adaptation response. The ESBP6 overexpressing strain carrying the LDH gene induced 20% increase in lactic acid production compared with the wild-type strain carrying the LDH gene under non-neutralizing conditions. These results indicate that overexpression of ESBP6 provides a novel and useful tool to improve lactic acid resistance and lactic acid production in yeast.

Does antibiotic resistance influence shiga-toxigenic Escherichia coli O26 and O103 survival to stress environments?

The presence of antibiotic-resistant bacteria in the food supply chain is a major concern. There is a great need to revalidate the effectiveness of the intervention strategies commonly used in food processing environments for multidrug-resistant strains. The purpose of this study was to determine the survival of antibiotic-resistant O26 and O103 Shiga-toxin producing Escherichia coli (STEC) strains to lactic acid (2.5, 3.5, 5%), sodium hypochlorite (0.2, 0.5, 1 ppm free chlorine), and heat (60, 61, 62.5 °C) treatments. Six strains from STEC serotypes O26 and O103 with three distinctive antibiotic-resistant profiles (susceptible, low and high resistance) were selected for the study. As expected, the rates of inactivation were faster at increasing biocide concentrations or temperature level. The Weibull model provided a better fit than the traditional log-linear model due to the appearance of nonlinear patterns. A 5% lactic acid treatment for 10 min reduced the population of all STEC strains by 5 log CFU/ml. Sodium hypochlorite treatment (1 ppm for 5 min) achieved a similar reduction. Thermal D values for O26 and O103 serotypes ranged from 0.37 to 2.09 and 0.37–1.71 min, respectively. No statistical differences (P > 0.05) in tolerance were found between the two STEC serotypes to the different treatments. The antibiotic profile was not related to the ability to tolerate any of the treatments. Only the susceptible strain showed a relative higher resistance to the lactic acid and lower resistance to sodium hypochlorite treatment. These results would contribute to assess the risk for the presence of STEC strains in food processing environments.

Arginine- and Polyamine-Induced Lactic Acid Resistance in Neisseria gonorrhoeae.

Microbe-derived lactic acid protects women from pathogens in their genital tract. The purpose of this study was to determine lactic acid susceptibility of Neisseria gonorrhoeae, and identify potential acid resistance mechanisms present in this pathogen. Tested in vitro, lactic acid killed all 10 gonococcal strains analyzed in a low pH-dependent manner. Full inactivation occurred at pH 4.5. At low pH, lactic acid treatment resulted in the entry of the DNA-binding fluorochrome propidium iodide into the microbial cells, suggesting that hydrogen ions from lactic acid compromise the integrity of the bacterial cell wall/membrane. Most likely, hydrogen ions also inactivate intracellular proteins since arginine rendered significant protection against lactic acid presumably through action of the gonococcal arginine decarboxylase, an enzyme located in the bacterial cytoplasm. Surprisingly, arginine also lessened lactic acid-mediated cell wall/membrane disruption. This effect is probably mediated by agmatine, a triamine product of arginine decarboxylase, since agmatine demonstrated a stronger protective effect on GC than arginine at equal molar concentration. In addition to agmatine, diamines cadaverine and putrescine, which are generated by bacterial vaginosis-associated microbes, also induced significant resistance to lactic acid-mediated GC killing and cell wall/membrane disruption. These findings suggest that the arginine-rich semen protects gonococci through both neutralization-dependent and independent mechanisms, whereas polyamine-induced acid resistance contributes to the increased risk of gonorrhea in women with bacterial vaginosis.

Improved stress resistance and ethanol production by segmental haploidization of the diploid genome in Saccharomyces cerevisiae

Saccharomyces cerevisiae strains from industrial and natural geographical environments are reported to show great variation in copy number of chromosomal regions. Such variation contributes to the mechanisms underlying adaptation to different environments. Here, we created and phenotypically analyzed segmentally haploidized strains, each harboring a deletion of one copy of approximately 100-300 kb of the left or right terminal region of 16 chromosomes in a diploid strain by using a PCR-mediated chromosomal deletion method. No haploidized strain of the 158-kb deleted right terminal region of chromosome III or the 172-kb deleted right terminal region of chromosome VI was produced; however, segmentally haploidized strains of the remaining 30 terminal regions were obtained. Among these 30 strains, two exhibited higher lactic acid resistance and two displayed higher thermo-tolerance at 41°C versus the host diploid strain. By contrast, four and two segmentally haploidized strains showed sensitivity to 6% lactic acid and low temperature at 13°C, respectively. The effect of the decreased copy number of the chromosomal terminal regions on ethanol production was analyzed. As compared with the host diploid strain, a 3.8% and 4.3% improvement in ethanol production in 10% glucose medium was observed for two strains in which one of two copies of the 197-kb left terminal region of chromosome V and one of two copies of the 195-kb left terminal region of chromosome X was deleted, respectively. These results indicate that artificial segmental haploidization might contribute to improvement of industrially important phenotypes and provide a new approach to breeding superior yeast strains.

GW26-e5360 The study on the exhaustive rabbits' ATPase, lactic acid and oxidation resistance by electroacupuncture intervention

In this paper, the study aims to pattern identification and treatment, Combination zusanli piont, shenshu point and match with pulses of electricity thorn observation motor ability, skeletal muscle oxidation resistance, ATP enzyme activity and lactic acid, to further explore the mechanism of action

Performance of stress resistant variants of Listeria monocytogenes in mixed species biofilms with Lactobacillus plantarum

Population diversity and the ability to adapt to changing environments allow Listeria monocytogenes to grow and survive under a wide range of environmental conditions. In this study, we aimed to evaluate the performance of a set of acid resistant L. monocytogenes variants in mixed-species biofilms with Lactobacillus plantarum as well as their benzalkonium chloride (BAC) resistance in these biofilms. L. monocytogenes LO28 wild type and acid resistant variants were capable of forming mixed biofilms with L. plantarum at 20°C and 30°C in BHI supplemented with manganese and glucose. Homolactic fermentation of glucose by L. plantarum created an acidic environment with pH values below the growth boundary of L. monocytogenes. Some of the variants were able to withstand the low pH in the mixed biofilms for a longer time than the WT and there were clear differences in survival between the variants which could not be correlated to (lactic) acid resistance alone. Adaptation to mild pH of liquid cultures during growth to stationary phase increased the acid resistance of some variants to a greater extent than of others, indicating differences in adaptive behaviour between the variants. Two variants that showed a high level of acid adaptation when grown in liquid cultures, showed also better performance in mixed species biofilms. There were no clear differences in BAC resistance between the wild type and variants in mixed biofilms. It can be concluded that acid resistant variants of L. monocytogenes show diversity in their adaptation to acidic conditions and their capacity to survive in mixed cultures and biofilms with L. plantarum.

Nuclear Localization of Haa1, Which Is Linked to Its Phosphorylation Status, Mediates Lactic Acid Tolerance in Saccharomyces cerevisiae

Improvement of the lactic acid resistance of the yeast Saccharomyces cerevisiae is important for the application of the yeast in industrial production of lactic acid from renewable resources. However, we still do not know the precise mechanisms of the lactic acid adaptation response in yeast and, consequently, lack effective approaches for improving its lactic acid tolerance. To enhance our understanding of the adaptation response, we screened for S. cerevisiae genes that confer enhanced lactic acid resistance when present in multiple copies and identified the transcriptional factor Haa1 as conferring resistance to toxic levels of lactic acid when overexpressed. The enhanced tolerance probably results from increased expression of its target genes. When cells that expressed Haa1 only from the endogenous promoter were exposed to lactic acid stress, the main subcellular localization of Haa1 changed from the cytoplasm to the nucleus within 5 min. This nuclear accumulation induced upregulation of the Haa1 target genes YGP1, GPG1, and SPI1, while the degree of Haa1 phosphorylation observed under lactic acid-free conditions decreased. Disruption of the exportin gene MSN5 led to accumulation of Haa1 in the nucleus even when no lactic acid was present. Since Msn5 was reported to interact with Haa1 and preferentially exports phosphorylated cargo proteins, our results suggest that regulation of the subcellular localization of Haa1, together with alteration of its phosphorylation status, mediates the adaptation to lactic acid stress in yeast.

Lactic acid resistance of Shiga toxin-producing Escherichia coli and multidrug-resistant and susceptible Salmonella Typhimurium and Salmonella Newport in meat homogenate

This study compared lactic acid resistance of individual strains of wild-type and rifampicin-resistant non-O157 Shiga toxin-producing Escherichia coli (STEC) and of susceptible and multidrug-resistant (MDR) and/or MDR with acquired ampC gene (MDR-AmpC) Salmonella against E. coli O157:H7. After inoculation of sterile 10% beef homogenate, lactic acid was added to a target concentration of 5%. Before acid addition (control), after acid addition (within 2 s, i.e. time-0), and 2, 4, 6 and 8 min after addition of acid, aliquots were removed, neutralized, and analyzed for survivors. Of wild-type and of rifampicin-resistant non-O157 STEC strains, irrespective of serogroup, 85.7% (30 out of 35 strains) and 82.9% (29 out of 35 strains), respectively, reached the detection limit within 0–6 min. Of Salmonella strains, 87.9% (29 out of 33 isolates) reached the detection limit within 0–4 min, irrespective of antibiotic resistance phenotype. Analysis of non-log-linear microbial survivor curves indicated that non-O157 STEC serogroups and MDR and susceptible Salmonella strains required less time for 4D-reduction compared to E. coli O157:H7. Overall, for nearly all strains and time intervals, individual strains of wild-type and rifampicin-resistant non-O157 STEC and Salmonella were less (P < 0.05) acid tolerant than E. coli O157:H7.

Disruption of multiple genes whose deletion causes lactic-acid resistance improves lactic-acid resistance and productivity in Saccharomyces cerevisiae

To create strains that have high productivity of lactic acid without neutralization, a genome-wide screening for strains showing hyper-resistance to 6% l-lactic acid (pH 2.6) was performed using the gene deletion collection of Saccharomyces cerevisiae. We identified 94 genes whose disruption led to resistance to 6% lactic acid in rich medium. We also found that multiple combinations of Δdse2, Δscw11, Δeaf3, and/or Δsed1 disruption led to enhanced resistance to lactic acid depending upon their combinations. In particular, the quadruple disruptant Δdse2Δscw11Δeaf3Δsed1 grew well in 6% lactic acid with the shortest lag phase. We then introduced an exogenous lactate dehydrogenase gene (LDH) into those single and multiple disruptants to evaluate their productivity of lactic acid. It was found that the quadruple disruptant displaying highest lactic-acid resistance showed a 27% increase of lactic-acid productivity as compared with the LDH-harboring wild-type strain. These observations suggest that disruption of multiple genes whose deletion leads to lactic-acid resistance is an effective way to enhance resistance to lactic acid, leading to high lactic-acid productivity without neutralization.

Selection of Lactobacillus plantarum strains for their use as starter cultures in Algerian olive fermentations

The aim of this research was to evaluate some technological traits of L. plantarum strains previously isolated from fermented olives. For this purpose, 11 strains were tested for their in vitro antibiotic susceptibility, resistance to low pH values, acidifying activity, proteolytic activity, haemolytic activity, lactic acid and exopolysaccharide production and resistance to freeze-drying .Collectively, the strains were susceptible to most of the antibiotics tested and showed survival at pH 2. Most strains showed high (1.035 ± 0.29 to 0.912 ± 0.21 mmol/l ± sd of lactic acid) or medium (0.556 ± 0.29 to 0.692 ± 0.18 mmol/l±sd) acidification activity with good proteolytic activity (1.49 ± 0.25 to 5.25 ± 0.11 mg L –1 tyrosine). None of the strains produced exopolysaccharides or haemolysis in sheep’s blood.

Biofilm Formation by Lactic Acid Bacteria and Resistance to Environmental Stress

We investigated the formation of biofilms by 3 type strains of lactic acid bacteria (LAB), Lactobacillus plantarum, Lactobacillus brevis and Lactobacillus fructivorans, as representatives of LAB that cause food deterioration or contamination. Lactobacillus plantarum subsp. plantarum JCM1149 and Lactobacillus brevis JCM1059 appeared to adhere and accumulate on glass cover slips. Lactobacillus fructivorans JCM1117 cells made thin cellophane-like biofilms, and most of the biofilm cells became longer than the planktonic cells. We tested the resistance of biofilm and planktonic L. plantarum subsp. plantarum JCM1149 cells to acetic acid and ethanol, which strongly inhibit the growth of bacteria and are important in food preservation. The biofilm cells were more resistant than the planktonic cells and the surfaces of the treated planktonic cells were badly damaged, whereas those of the biofilm cells were only slightly damaged. We isolated 43 LAB from onions and the biofolm cells of an isolate, L. plantarum M606 also had high resistance. These results demonstrate the significance of studying biofilms of LAB in the food industry.