Vacuum-packed lamb produced in Australia has a shelf-life of 80-90 days under export conditions (... more Vacuum-packed lamb produced in Australia has a shelf-life of 80-90 days under export conditions (-1 to 0 °C). However, access to some markets could involve >90 days transit time. Studies to understand the potential mechanisms of microbial spoilage of vacuum-packed lamb are, therefore, important to assist the development of shelf-life extension methods. Here, we investigated the effects of glucose on the shelf-life of vacuum-packed lamb. This was done by adding glucose (up to 4.64 mmol/kg) to the surface of meat and conducting a series of shelf-life trials, in which the sensorial qualities, bacterial growth, pH, and residual glucose and lactic acid were measured over time. Based on sensory analysis glucose extended the shelf-life, ranging from 8% to >76% increase relative to the control. Glucose reduced meat pH, potentially affecting the microbial community composition and the accumulation of spoilage metabolites. These results indicate that glucose plays an important role in microbial spoilage of vacuum-packed lamb possibly by pH reduction.
SummaryBacteria respond to osmotic stress by a substantial increase in the intracellular osmolali... more SummaryBacteria respond to osmotic stress by a substantial increase in the intracellular osmolality, adjusting their cell turgor for altered growth conditions. Using Escherichia coli as a model organism we demonstrate here that bacterial responses to hyperosmotic stress specifically depend on the nature of osmoticum used. We show that increasing acute hyperosmotic NaCl stress above ∼1.0 Os kg−1 causes a dose‐dependent K+ leak from the cell, resulting in a substantial decrease in cytosolic K+ content and a concurrent accumulation of Na+ in the cell. At the same time, isotonic sucrose or mannitol treatment (non‐ionic osmotica) results in a gradual increase of the net K+ uptake. Ion flux data are consistent with growth experiments showing that bacterial growth is impaired by NaCl at the concentration resulting in a switch from net K+ uptake to efflux. Microarray experiments reveal that about 40% of upregulated genes shared no similarity in their responses to NaCl and sucrose treatment, further suggesting specificity of osmotic adjustment in E. coli to ionic and non‐ionic osmotica. The observed differences are explained by the specificity of the stress‐induced changes in the membrane potential of bacterial cells highlighting the importance of voltage‐gated K+ transporters for bacterial adaptation to hyperosmotic stress.
Applied and Environmental Microbiology, Jun 2, 2020
Culture-based and culture-independent approaches were utilized to reveal bacterial community chan... more Culture-based and culture-independent approaches were utilized to reveal bacterial community changes on chicken carcasses at different processing steps and potential routes from the local processing environment. Current commercial processing effectively reduced bacterial loads on carcasses. Poultry processes have similar processes across facilities, but various processing arrangements and operating parameters could impact the bacterial transmission and persistence on carcasses differently. This study showed the use of a single tunnel incorporating scalding, defeathering and plucking may undesirably distribute the thermoduric bacteria, e.g., Campylobacter and Anoxybacillus , between the local environment and carcasses, whereas this does not occur when these steps are separated. The length of immersion and air chilling also impacted bacterial diversity on carcasses. Air chilling can transfer Pseudomonas from wall surfaces onto carcasses; this may subsequently influence chicken product shelf life. This study helps poultry processors understand the impact of current commercial processing and improve the chicken product quality and safety.
Proteomics-based approaches have been used in microbial taxonomy for the last several decades. Re... more Proteomics-based approaches have been used in microbial taxonomy for the last several decades. Recent improvements in instruments and software have led to the appearance of mass spectrometric fingerprinting and peptide survey approaches allowing for highly rapid and accurate taxonomic diagnoses suitable for high-throughput laboratories as well as means to deeply analyse entire proteomes. Taxonomy has an important role to play in microbiology being mainly for: 1) identification of pathogens performed in clinical diagnostic laboratories; 2) epidemiological strain typing; and 3) for diversity and bioprospecting studies in which bacterial names are used to encapsulate information. In the case of clinical diagnosis, a key aspect is rapidity and accuracy; for epidemiology, discrimination of strains in a reliable and meaningful way is required; while broader ecology-oriented applications of taxonomy rely on a robust classification system well served by ancillary data that is phenotypic, bi...
Mycotoxins are emerging toxins in the marine environment, which can co-occur with algal toxins to... more Mycotoxins are emerging toxins in the marine environment, which can co-occur with algal toxins to exert synergistic or antagonistic effects for human seafood consumption. The current study assesses the cytotoxicity of the algal toxin okadaic acid, shellfish, and dust storm-associated mycotoxins alone or in combination on human intestinal (HT-29) and neuroblastoma (SH-SY5Y) cell lines. Based on calculated IC50 (inhibitory concentration 50%) values, mycotoxins and the algal toxin on their own exhibited increased cytotoxicity in the order of sydowinin A < sydowinin B << patulin < alamethicin < sydowinol << gliotoxin ≈ okadaic acid against the HT-29 cell line, and sydowinin B < sydowinin A << alamethicin ≈ sydowinol < patulin, << gliotoxin < okadaic acid against the SH-SY5Y cell line. Combinations of okadaic acid–sydowinin A, –alamethicin, –patulin, and –gliotoxin exhibited antagonistic effects at low-moderate cytotoxicity, but became synergisti...
Vacuum-packed lamb produced in Australia has a shelf-life of 80-90 days under export conditions (... more Vacuum-packed lamb produced in Australia has a shelf-life of 80-90 days under export conditions (-1 to 0 °C). However, access to some markets could involve >90 days transit time. Studies to understand the potential mechanisms of microbial spoilage of vacuum-packed lamb are, therefore, important to assist the development of shelf-life extension methods. Here, we investigated the effects of glucose on the shelf-life of vacuum-packed lamb. This was done by adding glucose (up to 4.64 mmol/kg) to the surface of meat and conducting a series of shelf-life trials, in which the sensorial qualities, bacterial growth, pH, and residual glucose and lactic acid were measured over time. Based on sensory analysis glucose extended the shelf-life, ranging from 8% to >76% increase relative to the control. Glucose reduced meat pH, potentially affecting the microbial community composition and the accumulation of spoilage metabolites. These results indicate that glucose plays an important role in microbial spoilage of vacuum-packed lamb possibly by pH reduction.
SummaryBacteria respond to osmotic stress by a substantial increase in the intracellular osmolali... more SummaryBacteria respond to osmotic stress by a substantial increase in the intracellular osmolality, adjusting their cell turgor for altered growth conditions. Using Escherichia coli as a model organism we demonstrate here that bacterial responses to hyperosmotic stress specifically depend on the nature of osmoticum used. We show that increasing acute hyperosmotic NaCl stress above ∼1.0 Os kg−1 causes a dose‐dependent K+ leak from the cell, resulting in a substantial decrease in cytosolic K+ content and a concurrent accumulation of Na+ in the cell. At the same time, isotonic sucrose or mannitol treatment (non‐ionic osmotica) results in a gradual increase of the net K+ uptake. Ion flux data are consistent with growth experiments showing that bacterial growth is impaired by NaCl at the concentration resulting in a switch from net K+ uptake to efflux. Microarray experiments reveal that about 40% of upregulated genes shared no similarity in their responses to NaCl and sucrose treatment, further suggesting specificity of osmotic adjustment in E. coli to ionic and non‐ionic osmotica. The observed differences are explained by the specificity of the stress‐induced changes in the membrane potential of bacterial cells highlighting the importance of voltage‐gated K+ transporters for bacterial adaptation to hyperosmotic stress.
Applied and Environmental Microbiology, Jun 2, 2020
Culture-based and culture-independent approaches were utilized to reveal bacterial community chan... more Culture-based and culture-independent approaches were utilized to reveal bacterial community changes on chicken carcasses at different processing steps and potential routes from the local processing environment. Current commercial processing effectively reduced bacterial loads on carcasses. Poultry processes have similar processes across facilities, but various processing arrangements and operating parameters could impact the bacterial transmission and persistence on carcasses differently. This study showed the use of a single tunnel incorporating scalding, defeathering and plucking may undesirably distribute the thermoduric bacteria, e.g., Campylobacter and Anoxybacillus , between the local environment and carcasses, whereas this does not occur when these steps are separated. The length of immersion and air chilling also impacted bacterial diversity on carcasses. Air chilling can transfer Pseudomonas from wall surfaces onto carcasses; this may subsequently influence chicken product shelf life. This study helps poultry processors understand the impact of current commercial processing and improve the chicken product quality and safety.
Proteomics-based approaches have been used in microbial taxonomy for the last several decades. Re... more Proteomics-based approaches have been used in microbial taxonomy for the last several decades. Recent improvements in instruments and software have led to the appearance of mass spectrometric fingerprinting and peptide survey approaches allowing for highly rapid and accurate taxonomic diagnoses suitable for high-throughput laboratories as well as means to deeply analyse entire proteomes. Taxonomy has an important role to play in microbiology being mainly for: 1) identification of pathogens performed in clinical diagnostic laboratories; 2) epidemiological strain typing; and 3) for diversity and bioprospecting studies in which bacterial names are used to encapsulate information. In the case of clinical diagnosis, a key aspect is rapidity and accuracy; for epidemiology, discrimination of strains in a reliable and meaningful way is required; while broader ecology-oriented applications of taxonomy rely on a robust classification system well served by ancillary data that is phenotypic, bi...
Mycotoxins are emerging toxins in the marine environment, which can co-occur with algal toxins to... more Mycotoxins are emerging toxins in the marine environment, which can co-occur with algal toxins to exert synergistic or antagonistic effects for human seafood consumption. The current study assesses the cytotoxicity of the algal toxin okadaic acid, shellfish, and dust storm-associated mycotoxins alone or in combination on human intestinal (HT-29) and neuroblastoma (SH-SY5Y) cell lines. Based on calculated IC50 (inhibitory concentration 50%) values, mycotoxins and the algal toxin on their own exhibited increased cytotoxicity in the order of sydowinin A < sydowinin B << patulin < alamethicin < sydowinol << gliotoxin ≈ okadaic acid against the HT-29 cell line, and sydowinin B < sydowinin A << alamethicin ≈ sydowinol < patulin, << gliotoxin < okadaic acid against the SH-SY5Y cell line. Combinations of okadaic acid–sydowinin A, –alamethicin, –patulin, and –gliotoxin exhibited antagonistic effects at low-moderate cytotoxicity, but became synergisti...
Uploads
Papers by John Bowman