S-producing Bacteria Research Articles

Methanogens and Hydrogen Sulfide Producing Bacteria Guide Distinct Gut Microbe Profiles and Irritable Bowel Syndrome Subtypes.

Irritable bowel syndrome (IBS) includes diarrhea-predominant (IBS-D) and constipation-predominant (IBS-C) subtypes. We combined breath testing and stool microbiome sequencing to identify potential microbial drivers of IBS subtypes. IBS-C and IBS-D subjects from 2 randomized controlled trials (NCT03763175 and NCT04557215) were included. Baseline breath carbon dioxide, hydrogen (H 2 ), methane (CH 4 ), and hydrogen sulfide (H 2 S) levels were measured by gas chromatography, and baseline stool microbiome composition was analyzed by 16S rRNA sequencing. Microbial metabolic pathways were analyzed using Kyoto Encyclopedia of Genes and Genomes collection databases. IBS-C subjects had higher breath CH 4 that correlated with higher gut microbial diversity and higher relative abundance (RA) of stool methanogens, predominantly Methanobrevibacter , as well as higher absolute abundance of Methanobrevibacter smithii in stool. IBS-D subjects had higher breath H 2 that correlated with lower microbial diversity and higher breath H 2 S that correlated with higher RA of H 2 S-producing bacteria, including Fusobacterium and Desulfovibrio spp. The predominant H 2 producers were different in these distinct microtypes, with higher RA of Ruminococcaceae and Christensenellaceae in IBS-C/CH 4 + (which correlated with Methanobacteriaceae RA) and higher Enterobacteriaceae RA in IBS-D. Finally, microbial metabolic pathway analysis revealed enrichment of Kyoto Encyclopedia of Genes and Genomes modules associated with methanogenesis and biosynthesis of methanogenesis cofactor F420 in IBS-C/CH 4 + subjects, whereas modules associated with H 2 S production, including sulfate reduction pathways, were enriched in IBS-D. Our findings identify distinct gut microtypes linked to breath gas patterns in IBS-C and IBS-D subjects, driven by methanogens such as M. smithii and H 2 S producers such as Fusobacterium and Desulfovibrio spp, respectively.

Preparation of chitosan grafted caffeic acid coating and its effect on pompano (Trachinotus ovatus) preservation.

The present study aimed to investigate the preservative effect of chitosan-caffeic acid grafts coating (CS-g-CA) on the quality and microbial characteristics of pompano (Trachinotus ovatus) during iced storage. CS-g-CA was prepared by a 1-(3-dimethylaminopropyl)-3-ethylcarbodiimidehydro/N-hydroxysuccinimide coupling reaction. The grafting of CS-g-CA was confirmed by UV-visible and Fourier-transform infrared spectra. Samples were treated with distilled water (control), chitosan (CS), caffeic acid (CA) and CS-g-CA for 10min, respectively. Microbiological [total viable count (TVC), H2 S-producing bacteria count, Pseudomonas bacteria count], physicochemical indicators [water holding capacity (WHC), cooking loss, pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA), texture profile analysis, free amino acids] and sensory evaluation were investigated during ice storage at 4°C for up to 27 days. The results showed that the antioxidant and antibacterial activities of CS could be improved by grafting CA onto CS. CS-g-CA coating could greatly slow down the speed of water loss and maintain WHC. Furthermore, CS-g-CA coating showed superior antibacterial activities by inhibiting the growth of TVC, delayed the decline of flavor amino acids and reduced sensory change. In addition, CS-g-CA coating reduced lipid oxidation and protein degradation as indicated by the decrease in TBA and TVB-N, possibly as a result of the addition of CA into CS membrane significantly improving the antioxidant activity of CS. Compared with the control group, CS-g-CA coating had the optimal effect and could enhance the shelf-life of Trachinotus ovatus for at least another 9 days. © 2021 Society of Chemical Industry.

Oxidized Pork Induces Oxidative Stress and Inflammation by Altering Gut Microbiota in Mice.

Reduced digestibility of foods containing oxidized proteins and the subsequent excessive accumulation of undigested components in the colon may cause changes in the intestinal flora composition. This study evaluates the characteristics of this change and the potential adverse effects on organisms. Pork is cooked using sous-vide or at high temperature and pressure (HTP), then freeze-dried, resulting in different levels of oxidized damage. Mice are fed diets containing low- (LOP), medium- (MOP), or high-oxidative damage pork (HOP) for 12 weeks. HOP intake increases mice body weight, induces inflammatory response, and causes oxidative stress, as indicated by the accumulation of oxidative products. Increased serum LPS levels and downregulation of tight junction-related genes in the mucosa suggest mucosal barrier damage. Alterations in the cecal microbiota include reduced relative abundance of the mucin-degrading bacteria Akkermansia, beneficial bacteria Lactobacillus and Bifidobacterium, and H2 S-producing bacteria Desulfovibrio and increased relative abundance of the pro-inflammatory bacteria Escherichia-Shigella and pathobiont Mucispirillum. HOP intake causes the accumulation of oxidative products, increases body weight, damages the intestinal barrier, and induces oxidative stress and inflammatory response, likely by altering gut microbiota through protein oxidation (POX).

Effects of storage temperature on bacterial growth rates and community structure in fresh retail sushi

This study was conducted to assess the effects of different storage temperatures (4-20°C), on bacterial concentrations, growth rates and community structure in fresh retail sushi, a popular retail product with a claimed shelf life of 2-3days. The maximum specific growth rate based on aerobic plate count (APC) at 4°C was 0·06h-1 and displayed a sixfold increase (0·37h-1 ) at 20°C. Refrigeration resulted in no growth of hydrogen sulphide (H2 S)-producing bacteria, but this group had the strongest temperature response. The bacterial community structure was determined by PCR/DGGE (denaturing gradient gel electrophoresis). Multivariate analysis based on Bray-Curtis similarities demonstrated that temperature alone was not the major determinant for the bacterial community structure. The total concentration of aerobic bacteria was the variable that most successfully explained the differences between the communities. The dominating organisms, detected by sequencing of DNA bands excised from the DGGE gel, were Brochothrix thermosphacta and genera of lactic acid bacteria (LAB). The relationship between growth rates and storage temperatures clearly demonstrates that these products are sensitive to deviations from optimal storage temperature, possibly resulting in loss of quality during shelf life. Regardless of the storage temperature, the bacterial communities converged towards a similar structure and density, but the storage temperature determined how fast the community reached its carrying capacity. Little information is available on the microbial composition of ready-to-eat food that are prepared with raw fish, subjected to contamination during handling, and susceptible to microbial growth during cold storage. Moreover, the data are a good first possibility to simulate growth of APC, H2 S-producing bacteria and LAB under different temperature scenarios that might occur during production, distribution or storage.

Quorum Sensing Involved in the Spoilage Process of the Skin and Flesh of Vacuum-Packaged Farmed Turbot (Scophthalmus maximus) Stored at 4 °C.

Fish skin has both positive and negative effects on the shelf-life of the fish. This study aimed to investigate the spoilage process of the skin and flesh of refrigerated farmed turbot (Scophthalmus maximus) with vacuum packaging. Microbial community changes were analyzed by combining culture-dependent and culture-independent methods. The results indicated that the shelf-life of vacuum-packaged refrigerated turbot was 16 d; skin mucus was the interference factor of turbot quality. The culture-dependent analysis demonstrated that the total viable counts and the population of H2 S-producing bacteria, Pseudomonas spp., Enterobacteriaceae spp., and lactic acid bacteria in skin had a range of 0.45 to 1.40 log (CFU/g) higher than the microbial numbers in flesh after 16 d in storage. 16S high throughout sequencing results demonstrated that the compositions of spoilage microbes were similar in skin and flesh. Shewanella spp., followed by Carnobacterium spp., was the dominant spoilage organism at day 16. Quorum sensing (QS) signaling activity increased during the storage. Exogenous N-butanoyl-L-homoserinelactone(C4-HSL) and N-hexanoyl-Lhomoserine lactone (C6-HSL) significantly accelerated the spoilage process of refrigerated turbot, while the addition of 4, 5-Dihydroxypentane-2, 3-dione (DPD) prolonged the lag phase duration. Therefore, QS may be involved in the spoilage process of refrigerated turbot.

Impact of the O2 Concentrations on Bacterial Communities and Quality of Modified Atmosphere Packaged Pacific White Shrimp (Litopenaeus Vannamei)

The importance of spoilage-related bacteria in fresh Pacific white shrimp (Litopenaeus vannamei) under different modified atmospheres (MAs) at 4 °C and the effect of O2 were demonstrated in the current study. The changes of bacterial communities in MA-packed shrimp during cold storage were studied by a combined method of plate counts with isolation and identification. Three gas mixtures were applied: 80% CO2 /5% O2 /15% N2, 80% CO2 /10% O2 /10% N2 and 80% CO2 /20% O2, and unsealed packages of shrimp were used as the control. In addition, the TVB-N, pH, whiteness index, and sensory scores were also determined to evaluate the quality changes of shrimp. MA packaging effectively inhibited the increase of total psychrotrophic bacteria counts and H2 S-producing bacteria counts by about 1.7 and 2.1 log cycles, respectively. The growth of Gram-negative spoilage bacteria in shrimp, including Shewanella spp., Aeromonas spp., and Pseudomonas spp., was inhibited by MA packaging, but the growth rate of Gram-positive bacteria such as lactic acid bacteria (LAB) and Brochothrix spp. were less affected by MA as effectively as Gram-negative bacteria. In comparison with the MA-packaged samples, the counts of H2 S producers in shrimp under a CO2 -enriched atmosphere with 20% O2 were slightly lower than the count in samples under an atmosphere with 5% O2 . However, MA with 20% O2 led to higher concentrations of TVB-N, and lower whiteness values and sensory scores. The shelf life of shrimp under 80% CO2 /10% O2 /10% N2 has been prolonged by > 6 d in comparison with the control according to the sensory scores.

Validation of the H2S method to detect bacteria of fecal origin by cultured and molecular methods

Using biochemical and molecular methods, this research determined whether or not the H(2)S test did correctly identify sewage-contaminated waters by being the first to use culturing and molecular methods to identify the types and numbers of fecal indicator organisms, pathogens, and other microbes present in sewage samples with positive H(2)S test results. For the culture-based method, samples were analyzed for the presence of fecal bacteria by spread plating the sewage sample onto differential and selective media for Aeromonas spp., Escherichia coli, sulfite-reducing clostridia, H(2)S-producing bacteria, and Salmonella/Shigella spp. The isolates were then: (1) tested to determine whether they were H(2)S-producing organisms and (2) identified to the genus and species level using biochemical methods. The molecular method used to characterize the microbial populations of select samples was terminal restriction fragment length polymorphisms. These experiments on sewage provided evidence that positive H(2)S tests consistently contained fecal bacteria and pathogens. There were strong relationships of agreement between the organisms identified by both methods tested. This study is an important advance in microbial water quality detection since it is focused on the evaluation of a novel, low-cost, water microbiology test that has the potential to provide millions of people worldwide access to water quality detection technology. Of prime consideration in evaluating water quality tests is the determination of the test's accuracy and specificity, and this article is a fundamental step in providing that information.

Retardation of quality changes of Pacific white shrimp by green tea extract treatment and modified atmosphere packaging during refrigerated storage

The effect of modified atmosphere packaging (MAP) on the quality changes of Pacific white shrimp (Litopenaeus vannamei) treated with or without green tea extract (1g/L; GTE) in combination with or without ascorbic acid (0.05g/L; AA) during refrigerated storage of 10days was investigated. Shrimp without treatment stored under MAP had lowered psychrotrophic bacteria, enterobacteriaceae and H(2)S-producing bacteria count (P<0.05) but similar lactic acid bacteria count (P>0.05), in comparison with shrimp stored in air (control). The coincidental lowered rate of increase in pH, total volatile base (TVB) content and thiobarbituric acid reactive substances (TBARS) were obtained in shrimp stored under MAP (P<0.05). However, MAP slightly lowered melanosis formation and improved likeness score to some extent. When shrimp were treated with GTE and stored under MAP, the lower microbiological and chemical changes as well as the lowest melanosis formation were observed, compared to shrimp kept under MAP without treatment and the control (P<0.05). GTE treatment in combination with MAP could retard chemical changes and melanosis formation, regardless of AA incorporation (P>0.05). Nevertheless, GTE in combination with AA had higher inhibition on microbial growth and yielded the shrimp with higher likeness, compared with the other treatments (P<0.05). Therefore, shrimp treated with GTE in combination with AA prior to MAP had the lowest losses in quality during refrigerated storage.

Screening and identification of two Macrolactin S-producing bacteria from the sea

Objective:To isolate and screen active marine microorganisms from the East China Sea and to identify the phenotypes of the isolated strains.Methods:Thirty strains of bacteria isolated from the East China Sea were selected randomly,and the active strains were screened out by the anti-Escherichia coli model.The active strains were subjected to physiological and biochemical characteristics,salt-aggregation test,and 16S rDNA sequence analysis.Neighbor-joining trees were constructed by comparing the results of 16S rDNA sequences with sequences described in the BLAST server of the National Center for Biotechnology Information(NCBI);the strains were subsequently identified to genus level.Results:Strains F81612 and F201721 were screened out with the optimum salinities of 10% and 7.5%,respectively.Their morphology and biochemical characteristics were similar to those of Bacillus sp..16S rDNA sequence analysis showed that sequences of F81612 had a higher similarity to those of Bacillus subtilis;F201721 was similar to Bacillus amyloliquefaciens.Conclusion:Two Macrolactin S-producing strains have been screened out by the anti-Escherichia coli model,and they are identified as moderate halophilic Bacillus sp.

Effect of Brining, Modified Atmosphere Packaging, and Superchilling on the Shelf Life of Cod (Gadus morhua) Loins

The aim of these experiments was to evaluate the effect of brining, modified atmosphere packaging (MAP), and superchilling on the quality changes of cod loins as measured by microbial, sensory, and chemical analysis. Unbrined and brined (2.5 +/- 1.0% NaCl) cod loins were kept in styrofoam boxes (air) and under modified atmosphere (MA, CO(2)/O(2)/N(2): 50/5/45) at 0, -2, and -3.6 degrees C. Samples were examined over a 4-wk period. Total viable psychrotrophic counts and counts of H(2)S-producing bacteria reached higher numbers in the air-packed brined fish at -2 and -3.6 degrees C than in comparable unbrined groups, being significantly different (P < 0.05) at the lower temperature. However, lower counts of these bacteria were obtained in the brined MAP fish than in comparable unbrined fish. Counts of Photobacterium phosphoreum increased most rapidly in air- and MA-packed loins kept at 0 degrees C. Lower counts were found at superchilled temperatures. According to sensory analysis the shelf life of unbrined air-packed loins was about 11 d at 0 degrees C and 14 to 15 d at -2 degrees C. The shelf life of MA-packed unbrined loins was about 14 to 15 d at 0 degrees C but 21 d at -2 degrees C. Thus, synergism of combined superchilling (-2 degrees C) and MA led to a considerable shelf life increase for unbrined loins despite the fact that processing and packaging took place 4 to 5 d post-catch. The shelf life of air-packed brined loins at -2 degrees C was 12 to 15 d but only 13 d under MA. The same synergistic effect did therefore not apply to brined loins as with unbrined ones.

Melanosis and Quality Changes of Pacific White Shrimp (Litopenaeus vannamei) Treated with Catechin during Iced Storage

Melanosis, microbiological, chemical, and physical changes of Pacific white shrimp (Litopenaeus vannamei) treated with catechin were monitored during iced storage of 10 days. Whole shrimp treated with catechin solution (0.05 or 0.1%) had retarded growth of psychrophilic bacteria and spoilage microorganisms including H(2)S-producing bacteria and enterobacteriaceae throughout storage in comparison with the control and those treated with 1.25% sodium metabisilfite (SMS) (P < 0.05). The lower increases in pH and total volatile base (TVB) content were obtained in the shrimp treated with catechin solution at both levels, compared with those of other samples (P < 0.05). Lipid oxidation, loss in freshness and melanosis were lowered by catechin treatment. In general, the efficacy of catechin in lowering melanosis and quality losses increased with increasing levels used. Additionally, catechin (0.01, 0.05, and 0.1% (w/v)) showed inhibitory activity toward polyphenoloxidase (PPO) of Pacific white shrimp in a dose-dependent manner. Therefore, catechin can be used as a promising melanosis inhibitor as well as an antimicrobial and an antioxidant in ice-stored shrimp.

Potential of Oregano Essential Oil and MAP to Extend the Shelf Life of Fresh Swordfish: A Comparative Study with Ice Storage

The present study evaluated the effect of modified atmosphere packaging (MAP, 5% O(2)/50% CO(2)/45% N(2); treatment M), the addition of oregano oil (0.1%, v/w; treatment AO) as a natural preservative, as well as their combination (treatment MO) on the quality and shelf life extension of fresh Mediterranean swordfish fillets during a refrigerated storage (4 degrees C) period of 18 d. Simultaneously, swordfish fillets were stored under aerobic conditions (control treatment A, 4 degrees C) and on ice (usual commercial method of preservation, treatment I, 0 degrees C). Among the 5 treatments examined in the present study, the most effective one to inhibit the microbial and sensory spoilage proved to be the MO treatment, achieving a shelf life extension of 8 to 9 d. The dominant bacteria in the microflora of swordfish, irrespective of treatment, were the Pseudomonads and the H(2)S-producing bacteria, while both lactic acid bacteria (LAB) and the Enterobacteriaceae produced the lowest populations in swordfish samples kept on ice. Among the chemical indices examined, thiobarbituric acid (TBA) values showed no specific trend of lipid oxidation for swordfish, irrespective of treatment. Final trimethylamine nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N) values for treatments, A, AO, M, and MO ranged between 1.33 and 14.29 mg N/100 g and 14.11 to 55.52 mg N/100 g, respectively, whereas for I samples they remained almost unchanged during storage. Sensory analysis (taste attribute) correlated well with microbiological analysis, indicating a shelf life of approximately 5 to 6 d for control, 10 to 11 d for AO, 12 d for I, 13 d for M, and 14 d for MO samples.

Muscle Quality and Storage Stability of Farmed Cod (Gadus morhua L.) Compared to Wild Cod

Quality characteristics of farmed and wild cod were compared during ice storage by measuring pH, water content, water-holding capacity (WHC), trimethylamine oxide (TMAO), trimethylamine (TMA), aerobic plate count (APC), as well as numbers of H2 S-producing bacteria (SPB) and Photobacterium phosphoreum. pH and water content were higher in wild cod than in farmed cod. WHC were similar for both groups until the last sampling, where farmed cod had a significantly higher WHC than wild cod. The TMAO level in farmed cod was only 5–10% of that found in wild cod. APC increased more rapidly in wild cod than in farmed cod, resulting in a 2 log units difference at the end of the storage period. P. phosphoreum were found in higher numbers in wild cod than in farmed cod, and SPB were not detected in farmed cod. These results might indicate that farmed cod have a slightly longer shelf life than wild caught cod.

The antimicrobial effect of a triclosan/copolymer dentifrice on oral microorganisms in vivo

The authors compared the in vivo antimicrobial effects on microorganisms from dental plaque, saliva and the tongue in subjects who used a triclosan/copolymer dentifrice and a fluoride dentifrice (control). The authors assigned 15 subjects randomly to the control dentifrice or the triclosan/copolymer dentifrice for twice-daily use for one week. They collected samples of plaque, saliva and tongue scrapings six and 12 hours after the final brushing. They analyzed colony-forming units of Veillonella species, Fusobacteria species, total cultivable anaerobes and hydrogen sulfide (H(2)S)-producing bacteria. A one-week washout followed. The authors repeated the protocol with the second dentifrice. The results showed no differences at baseline. Significant reductions (88 to 96 percent) in oral anaerobic bacteria were observed in the triclosan/copolymer group six and 12 hours after brushing compared with the control group (P = .001). Fusobacteria decreased by 77 to 92 percent and Veillonella decreased by 84 to 89 percent six and 12 hours after brushing in the triclosan/copolymer group versus the control group. The triclosan/copolymer group also demonstrated a significant decrease in H(2)S-producing bacteria six and 12 hours after brushing (74 to 85 percent) (P = .001). Brushing with the triclosan/copolymer dentifrice resulted in significant reductions in microorganisms from the three sites compared with the control dentifrice. The triclosan/copolymer dentifrice produced sustained effects on oral bacteria for 12 hours.