Changes in the Microflora of Irradiated Petrale Sole (Eopsetta jordani) Fillets Stored Aerobically at 0.5 C

The microfloral changes on irradiated petrale sole fillets during aerobic (packaged with oxygen-permeable film), refrigerated storage were determined by the identification of bacterial and yeast isolates to the generic level. The samples were irradiated at 0.0, 0.1, 0.15, 0.2, 0.3, and 0.4 Mrad by use of a cobalt-60 gamma source, were stored at 0.5 C, and were examined periodically for spoilage, total microbial population, and composition. The preirradiation flora of the fresh fillets consisted of coryneforms, Achromobacter, Micrococcus, Flavobacterium, Pseudomonas, and Lactobacillus. Immediately after irradiation, Micrococcus, Achromobacter, coryneforms, and Bacillus were predominant. The flora of the nonirradiated fillets at the time of spoilage consisted of Pseudomonas and Achromobacter. The flora of the irradiated fillets at the time of spoilage consisted of Achromobacter and Trichosporon.     

Application of Replica Plating and Computer Analysis for Rapid Identification of Bacteria in Some Foods: II. Analysis of Microbial Flora in Irradiated Dover Sole (Microstomus pacificus)

This investigation was carried out to determine the nature of the microbial flora shifts in dover sole as a result of irradiation and storage at 6 C. The relationship was determined between the microorganisms which initially survive irradiation and those making up the final spoilage flora. A total of 2,723 isolates were examined by use of the replica-plating and computer analysis method. The spoilage of the unirradiated control samples during storage at 6 C was almost entirely due to the growth of Pseudomonas. This group, which occupied 25% of the fresh flora, grew to nearly 100% in 2 days of storage. In contrast, irradiation doses of 0.1, 0.2, 0.3, and 0.4 Mrad favored the growth of Achromobacter and yeasts. The Micrococcus, which survived radiation, did not grow at 6 C. At 0.5 Mrad, spoilage of fish samples was due entirely to the growth of yeasts.     

Effect of gamma Irradiation on the Microflora of Freshwater Fish: II. Generic Identification of Aerobic Bacteria from Yellow Perch Fillets

Studies on the generic identification of bacteria isolated from nonirradiated and irradiated (0.3 and 0.6 Mrad) yellow perch fillets during the course of microbial spoilage have been conducted. After the enumeration and tabulation of macrocolonies on petri dish cultures obtained from fillets, isolates were examined and keyed out essentially according to modified morphological and biochemical protocols of Shewan. Identification was further confirmed through reference to Bergey's Manual. Data obtained from each isolate were coded and recorded on IBM cards to facilitate identification. Total aerobic microbial plate counts obtained from nonirradiated perch before storage ranged from 10⁵ to 10⁶ microorganisms per gram of fish. Organisms isolated from these fillets, in order of decreasing number, consisted of Achromobacter, Alcaligenes, Pseudomonas, Brevibacterium, Micrococcus, Flavobacterium, Bacillus, Sarcina, Microbacterium, Corynebacterium, yeasts, Lactobacillus, Vibrio, Aeromonas, and a few Proteus and Escherichia cells. During storage and as spoilage progressed, the flora shifted and the pseudomonads became predominant. Irradiation of fillets to 0.3 and 0.6 Mrad reduced the aforementioned flora to the Achromobacter-Alcaligenes group, which constituted the residual flora throughout fillet storage.     

Comparative Effects of Chlortetracycline,Freezing, and γ Radiation on Microbial Population of Ocean Perch

The microbial populations in chlortetracycline (CTC)-treated (50, 100, 200, and 500 ppm), frozen (-15 C), and irradiated (0.1 Mrad) ocean perch (Sebastodes alutus) were compared. The control sample spoiled at 7 C, primarily because of the growth of Pseudomonas. Irradiation changed this to Achromobacter-dominated spoilage. Freezing or CTC treatment altered the spoilage pattern very little. CTC was particularly effective against ultraviolet fluorescent Pseudomonas species at the higher concentrations. Freezing and CTC were not effective against “coryneforms.”     

Effect of γ Irradiation on the Microflora of Freshwater Fish: II. Generic Identification of Aerobic Bacteria from Yellow Perch Fillets1

Studies on the generic identification of bacteria isolated from nonirradiated and irradiated (0.3 and 0.6 Mrad) yellow perch fillets during the course of microbial spoilage have been conducted. After the enumeration and tabulation of macrocolonies on petri dish cultures obtained from fillets, isolates were examined and keyed out essentially according to modified morphological and biochemical protocols of Shewan. Identification was further confirmed through reference to Bergey''s Manual. Data obtained from each isolate were coded and recorded on IBM cards to facilitate identification. Total aerobic microbial plate counts obtained from nonirradiated perch before storage ranged from 10⁵ to 10⁶ microorganisms per gram of fish. Organisms isolated from these fillets, in order of decreasing number, consisted of Achromobacter, Alcaligenes, Pseudomonas, Brevibacterium, Micrococcus, Flavobacterium, Bacillus, Sarcina, Microbacterium, Corynebacterium, yeasts, Lactobacillus, Vibrio, Aeromonas, and a few Proteus and Escherichia cells. During storage and as spoilage progressed, the flora shifted and the pseudomonads became predominant. Irradiation of fillets to 0.3 and 0.6 Mrad reduced the aforementioned flora to the Achromobacter-Alcaligenes group, which constituted the residual flora throughout fillet storage.     

Pseudomonads and achromobacters in the spoilage of irradiated haddock of different preirradiation quality

The effect of initial quality of fish on postirradiation (100 krad) changes in the bacterial flora of haddock fillets during aerobic storage at 3 C has been investigated, with emphasis on the Pseudomonas and Achromobacter groups. The quality was related to the length of time the eviscerated fish had been stored in ice prior to filleting. Increased numbers of organisms, in particular Pseudomonas putrefaciens, were found initially on fillets cut from older fish. Pseudomonads were reduced by 2 to 3 log orders by irradiation, and achromobacters and gram-positive isolates predominated in the immediate postirradiation flora. Little difference could be detected in either types or relative proportions of organisms occurring during storage of unirradiated fish of different quality. Pseudomonads outgrew achromobacters and dominated the spoilage flora in all cases. After spoilage, however, the growth rate of pseudomonads declined markedly. In irradiated fish, achromobacters predominated throughout storage. In fish of better initial quality, bacterial numbers were 1 to 2 log orders higher at spoilage than in their unirradiated counterparts and in the poorer quality of irradiated samples. The increased number of organisms was accompanied by a radical change in the character of the predominant achromobacters. Pseudomonads were found to increase in numbers during storage of irradiated fish, in particular in poorer quality fish on which they were initially present in higher numbers. Detection of pseudomonads, even when present in high numbers, was found to be limited by the identification techniques normally used.     

Microbial Flora of Irradiated Dungeness Crabmeat and Pacific Oysters

The microorganisms in Dungeness crabmeat (Cancer magister) and Pacific oysters (Crassostrea gigas) were identified by the replica-plating and computer analysis method. The initial flora of the shellfish and the flora change during storage at 7 C were determined. The microbial flora shifts in both shellfish were also determined after irradiation at 0.1 and 0.4 Mrad and during subsequent storage at 7 C. The Achromobacter species predominated in the initial flora of crabmeat (77.0%). The predominant position of this group increased to 99.2% after 0.1 Mrad and 100% after 0.4 Mrad. A large percentage of Lactobacillus was detected in oysters (55.0%). The Lactobacillus species were the predominant survivors after 0.1 Mrad (92.4%) but the predominant survivors after 0.4 Mrad were Achromobacter species (99.3%).     

Processing Environment and Ingredients Are Both Sources of Leuconostoc gelidum,Which Emerges as a Major Spoiler in Ready-To-Eat Meals

Mesophilic and psychrotrophic organism viable counts, as well as high-throughput 16S rRNA gene-based pyrosequencing, were performed with the aim of elucidating the origin of psychrotrophic lactic acid bacteria (LAB) in a ready-to-eat (RTE) meal manufacturing plant. The microbial counts of the products at the end of the shelf life were greatly underestimated when mesophilic incubation was implemented due to overlooked, psychrotrophic members of the LAB. Pseudomonas spp., Enterobacteriaceae, Streptococcaceae, and Lactobacillus spp. constituted the most widespread operational taxonomic units (OTUs), whereas Leuconostoc gelidum was detected as a minor member of the indigenous microbiota of the food ingredients and microbial community of the processing environment, albeit it colonized samples at almost every sampling point on the premises. However, L. gelidum became the most predominant microbe at the end of the shelf life. The ability of L. gelidum to outgrow notorious, spoilage-related taxa like Pseudomonas, Brochothrix, and Lactobacillus underpins its high growth dynamics and severe spoilage character under refrigeration temperatures. The use of predicted metagenomes was useful for observation of putative gene repertoires in the samples analyzed in this study. The end products grouped in clusters characterized by gene profiles related to carbohydrate depletion presumably associated with a fast energy yield, a finding which is consistent with the fastidious nature of highly competitive LAB that dominated at the end of the shelf life. The present study showcases the detrimental impact of contamination with psychrotrophic LAB on the shelf life of packaged and cold-stored foodstuffs and the long-term quality implications for production batches once resident microbiota are established in the processing environment.     

Studies on production of alcoholic beverages from some tropical fruits

The varieties of alcoholic beverages from watermelon; watermelon-banana and watermelon-pineapple mixtures were produced by using monoculture and mixed culture fermentation techniques. Three yeast species, namely, Saccharomyces cerevisiae, Kleochera apicalata, Torulospora delbruckii and four bacterial species Leuconostoc oenos, Lactobacillus Sp, Micrococcus luteus and Streptococcus lactis were identified during the study. The daily succession of these organisms in the various fermenting samples differed in cell mass and occurrence due to their different growth conditions and factors present. A higher bacterial load (3.9 ± 0.2-4.4 ± 0.3) log (cfu) ml^?1 than yeast (2.8 ± 00-4.6 ± 0.4) log (cfu) ml^?1 counts was observed in the mixed culture fermentation, while in the monoculture fermentation, a higher yeast load (4.3 ± 0.3-4.7 ± 0.2) log (cfu) ml^?1 than bacterial loads (2.7 ± 0.1-4.1 ± 0.3) log (cfu) ml^?1 counts was recovered. The results obtained from the present study indicated that monoculture-fermented beverages were of better quality as compared to the mixed culture fermented ones. The monoculture-fermented beverage from watermelon-pineapple mixture was ranked as the best alcoholic beverage based on sensory evaluation score.     

Analyzing the relation between the microbial diversity of DaQu and the turbidity spoilage of traditional Chinese vinegar

Vinegar is a traditional fermented condiment, and the microbial diversity of DaQu makes the quality of vinegar products. Recently, turbidity spoilage of vinegar sharply tampered with the quality of vinegar. In this study, the relation between the microbial diversity of DaQu and turbidity spoilage of vinegar was analyzed by plating technique, PCR–denaturing gradient gel electrophoresis (DGGE), and high-performance liquid chromatography (HPLC). The 16S rRNA sequencing and DGGE analysis indicated that Bacillus (Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus thuringiensis) and Lactobacillus (including Lactobacillus acidipiscis and Lactobacillus pobuzihii) species were the dominant contaminants in vinegar products. Meanwhile, DGGE analysis showed that the dominant bacteria in DaQu belonged to genera Bacillus, Lactobacillus, Pseudomonas, Weissella, Saccharopolyspora, Enterobacter, and Pantoea. However, only two yeast species (Pichia kudriavzevii and Saccharomycopsis fibuligera) and seven mold species including Aspergillus oryzae, Aspergillus niger, Aspergillus candidus, Rhizopus microspores, Eurotium herbariorum, Absidia corymbifera, and Eupenicillium javanicum were detected in the DaQu. The population level of fungi was below 5 log CFU/g in DaQu. The chemical and physical properties of vinegar and sediments were also determined. On the basis of a combined microbial diversity-chemical analysis, we demonstrated that turbidity spoilage of vinegar was a result of cooperation among the low population level and abundance of fungal species in DaQu, the suitable climate conditions, and the contaminants in vinegar. This is the first report to analyze the relation between the microbial diversity of DaQu and turbidity spoilage of vinegar.     

Comparative Effects of Chlortetracycline, Freezing, and γ Radiation on Microbial Population of Ocean Perch

The microbial populations in chlortetracycline (CTC)-treated (50, 100, 200, and 500 ppm), frozen (-15 C), and irradiated (0.1 Mrad) ocean perch (Sebastodes alutus) were compared. The control sample spoiled at 7 C, primarily because of the growth of Pseudomonas. Irradiation changed this to Achromobacter-dominated spoilage. Freezing or CTC treatment altered the spoilage pattern very little. CTC was particularly effective against ultraviolet fluorescent Pseudomonas species at the higher concentrations. Freezing and CTC were not effective against "coryneforms."     

Bacteriology of Spoilage of Fish Muscle: II. Incidence of Spoilers During Spoilage1

A test medium consisting of a sterile raw press juice from fish muscle was used to determine the incidence of spoilage bacteria on stored fillets of English sole (Parophrys vetulus). The initial load of spoilers was shown to be consistently below 10%. This percentage rose but slightly toward the middle of the spoilage runs, and actually declined when spoilage was most apparent both organoleptically and chemically. Further evidence implicating the Pseudomonas and Achromobacter groups in the spoilage of fresh fish is presented.     

Bacteriology of Spoilage of Fish Muscle: III. Characterization of Spoilers

A total of 807 bacterial isolates from fresh and spoiling fillets of English sole (Parophrys vetulus) stored at 5 C were classified as to genus and tested for various biochemical activities, including the ability to spoil sterile muscle press juice at 5 C. Production of off-odor, volatile reducing substances, and trimethylamine was used to estimate spoilage. It was found that (i) spoilers could be distinguished from nonspoilers on the basis of the juice spoilage test, (ii) differentiation between spoilers and nonspoilers could not be achieved by means of the usual biochemical tests, (iii) no micrococci, flavobacteria, and “coryneforms” were spoilers, (iv) certain specific subgroups of the genus Pseudomonas consisted exclusively of spoilers whereas others were inactive, (v) the genus Achromobacter likewise consisted of spoilers and nonspoilers, and (vi) “coliforms” could produce spoilage. It was concluded that a method is now available to determine directly and unequivocally the role played in spoilage by various bacterial groups and that it is no longer necessary to rely on indirect evidence.     

Effect of γ Irradiation on the Microflora of Freshwater Fish: III. Spoilage Patterns and Extension of Refrigerated Storage Life of Yellow Perch Fillets Irradiated to 0.1 and 0.2 Megarad1

Maximal shelf life was determined and microbial flora were compared for irradiated (0.1 and 0.2 Mrad) and nonirradiated yellow perch fillets stored at 1 C. Shelf life was estimated by organoleptic determinations. Microbiological studies included determination of the effects of irradiation on the total aerobic microbial population, lag phase, and rate of growth. Genera of organisms isolated from fillets through the course of microbial spoilage were identified, and the proteolytic activity of the organisms was determined. Plate counts for fish prior to irradiation showed the presence of approximately 10(6) organisms per g of sample. Irradiation to 0.1 and 0.2 Mrad produced 1.4 and 3 logarithm reductions of the initial count, respectively. Irradiation to 0.1 and 0.2 Mrad approximately doubled the product's shelf life. Organisms initially isolated from the nonirradiated fillets, in order of decreasing number, consisted of Flavobacterium, Micrococcus-Sarcina, Achromobacter-Alcaligenes-Mima, Pseudomonas, Microbacterium, Vibrio, Bacillus, Corynebacterium, Lactobacillus, Brevibacterium, and Aeromonas. By the 6th and 9th days of fillet storage, Pseudomonas and the Achromobacter group were the predominant organisms. All members of the genus Flavobacterium, but not all members of the genus Pseudomonas, were proteolytically active on raw fish juice-agar and skim milk-agar media. The Achromobacter group was found to be nonproteolytic on both media. Residual flora of fillets irradiated to 0.1 and 0.2 Mrad consisted of the Achromobacter group, Lactobacillus, Micrococcus-Sarcina, and Bacillus. Their sequence in predominance, however, varied with dose level. Not all proteolytic bacteria in the fillets were eliminated by 0.1 and 0.2 Mrad; proteolytic Micrococcus-Sarcina survived these treatments.     

Bacterial Communities in Semen from Men of Infertile Couples: Metagenomic Sequencing Reveals Relationships of Seminal Microbiota to Semen Quality

Some previous studies have identified bacteria in semen as being a potential factor in male infertility. However, only few types of bacteria were taken into consideration while using PCR-based or culturing methods. Here we present an analysis approach using next-generation sequencing technology and bioinformatics analysis to investigate the associations between bacterial communities and semen quality. Ninety-six semen samples collected were examined for bacterial communities, measuring seven clinical criteria for semen quality (semen volume, sperm concentration, motility, Kruger''s strict morphology, antisperm antibody (IgA), Atypical, and leukocytes). Computer-assisted semen analysis (CASA) was also performed. Results showed that the most abundant genera among all samples were Lactobacillus (19.9%), Pseudomonas (9.85%), Prevotella (8.51%) and Gardnerella (4.21%). The proportion of Lactobacillus and Gardnerella was significantly higher in the normal samples, while that of Prevotella was significantly higher in the low quality samples. Unsupervised clustering analysis demonstrated that the seminal bacterial communities were clustered into three main groups: Lactobacillus, Pseudomonas, and Prevotella predominant group. Remarkably, most normal samples (80.6%) were clustered in Lactobacillus predominant group. The analysis results showed seminal bacteria community types were highly associated with semen health. Lactobacillus might not only be a potential probiotic for semen quality maintenance, but also might be helpful in countering the negative influence of Prevotella and Pseudomonas. In this study, we investigated whole seminal bacterial communities and provided the most comprehensive analysis of the association between bacterial community and semen quality. The study significantly contributes to the current understanding of the etiology of male fertility.     

Bacteriology of Spoilage of Fish Muscle: I. Sterile Press Juice as a Suitable Experimental Medium

A sterile raw fish muscle press juice, diluted 1:4 with saline, has been prepared. This dilution greatly facilitated Seitz filtration and affected the spoilage properties of the medium only negligibly. At 5.5 C, the spoilage pattern of naturally contaminated diluted juice was almost identical to that of naturally contaminated fillets. This was shown by comparing the quantitative and qualitative aspects of the bacterial flora on the two substrates and by measuring the production of volatile reducing substances (VRS) and of trimethylamine (TMA). With the sterile raw muscle press juice, some preliminary data showed that individual members of the genera Achromobacter and Pseudomonas differ markedly in their spoilage capabilities: some grew but did not produce spoilage detectable either organoleptically or chemically; others gave rise to strong off odors and to high levels of VRS and TMA.     

Effect of Oxygen Tension on the Spoilage Microflora of Irradiated and Non-irradiated Haddock (Melanogrammus aeglefinus) Fillets

S ummary . The spoilage microflora of irradiated and non-irradiated air packed or vacuum packed haddock fillets was identified after storage of the fillets at 35°F. With the non-irradiated fillets, both air packed and vacuum packed, the spoilage flora was predominantly pseudomonads. With the irradiated fillets, the spoilage flora of the air packed samples was chiefly achromobacter; that of the vacuum packed samples was chiefly lactobacilli (or possibly Microbacterium thermosphactum ).     

Dynamics of Vaginal Bacterial Communities in Women Developing Bacterial Vaginosis, Candidiasis, or No Infection, Analyzed by PCR-Denaturing Gradient Gel Electrophoresis and Real-Time PCR

The microbial flora of the vagina plays a major role in preventing genital infections, including bacterial vaginosis (BV) and candidiasis (CA). An integrated approach based on PCR-denaturing gradient gel electrophoresis (PCR-DGGE) and real-time PCR was used to study the structure and dynamics of bacterial communities in vaginal fluids of healthy women and patients developing BV and CA. Universal eubacterial primers and Lactobacillus genus-specific primers, both targeted at 16S rRNA genes, were used in DGGE and real-time PCR analysis, respectively. The DGGE profiles revealed that the vaginal flora was dominated by Lactobacillus species under healthy conditions, whereas several potentially pathogenic bacteria were present in the flora of women with BV. Lactobacilli were the predominant bacterial population in the vagina for patients affected by CA, but changes in the composition of Lactobacillus species were observed. Real-time PCR analysis allowed the quantitative estimation of variations in lactobacilli associated with BV and CA diseases. A statistically significant decrease in the relative abundance of lactobacilli was found in vaginal fluids of patients with BV compared to the relative abundance of lactobacilli in the vaginal fluids of healthy women and patients with CA.     

Chemical and Sensory Changes Associated with Microbial Flora of Mediterranean Boque (Boops boops) Stored Aerobically at 0, 3, 7, and 10°C

The development of a microbial population and changes in the physicochemical and sensorial characteristics of Mediterranean boque (Boops boops), called gopa in Greece, stored aerobically at 0, 3, 7, and 10°C were studied. Pseudomonads and Shewanella putrefaciens were the dominant bacteria at the end of the storage period, regardless of the temperature tested. Enterobacteria and Brochothrix thermosphacta also grew, but their population density was always 2 to 3 log₁₀ CFU g⁻¹ less than that of pseudomonads. The concentration of potential indicators of spoilage, glucose and lactic acid, decreased while that of the α-amino groups increased during storage. The concentrations of these carbon sources also decreased on sterile fish blocks inoculated with strains isolated from fish microbial flora. The organic acid profile of sterile fish blocks inoculated with the above-mentioned bacteria and that of naturally spoiled fish differed significantly. An excellent correlation (r = −0.96) between log₁₀ counts of S. putrefaciens or Pseudomonas bacteria with freshness was observed in this study.     

Exploring the Sources of Bacterial Spoilers in Beefsteaks by Culture-Independent High-Throughput Sequencing

Microbial growth on meat to unacceptable levels contributes significantly to change meat structure, color and flavor and to cause meat spoilage. The types of microorganisms initially present in meat depend on several factors and multiple sources of contamination can be identified. The aims of this study were to evaluate the microbial diversity in beefsteaks before and after aerobic storage at 4°C and to investigate the sources of microbial contamination by examining the microbiota of carcasses wherefrom the steaks originated and of the processing environment where the beef was handled. Carcass, environmental (processing plant) and meat samples were analyzed by culture-independent high-throughput sequencing of 16S rRNA gene amplicons. The microbiota of carcass swabs was very complex, including more than 600 operational taxonomic units (OTUs) belonging to 15 different phyla. A significant association was found between beef microbiota and specific beef cuts (P<0.01) indicating that different cuts of the same carcass can influence the microbial contamination of beef. Despite the initially high complexity of the carcass microbiota, the steaks after aerobic storage at 4°C showed a dramatic decrease in microbial complexity. Pseudomonas sp. and Brochothrix thermosphacta were the main contaminants, and Acinetobacter, Psychrobacter and Enterobacteriaceae were also found. Comparing the relative abundance of OTUs in the different samples it was shown that abundant OTUs in beefsteaks after storage occurred in the corresponding carcass. However, the abundance of these same OTUs clearly increased in environmental samples taken in the processing plant suggesting that spoilage-associated microbial species originate from carcasses, they are carried to the processing environment where the meat is handled and there they become a resident microbiota. Such microbiota is then further spread on meat when it is handled and it represents the starting microbial association wherefrom the most efficiently growing microbial species take over during storage and can cause spoilage.