I.B. ZABALA DÍAZ

Texas A&M University

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Steven C. Ricke

University of Wisconsin–Madison

C.A. Froelich

St. Jude Children's Research Hospital

J. Allen Byrd

Southern Plains Agricultural Research Center

S.G. Birkhold

Texas A&M University

L.F. Kubena

Southern Plains Agricultural Research Center

Steven C. Ricke

University of Arkansas at Fayetteville

Zoë Howard

Health Education England

R.W. Moore

University of Arkansas at Fayetteville

A.M. ERICKSON

Texas A&M University

D. J. Nisbet

Agricultural Research Service

Cooperative Institutions

Texas A&M University

United States Department of Agriculture

Southern Plains Agricultural Research Center

Agricultural Research Service

University of Arkansas at Fayetteville

Mitchell Institute

Texas A&M University System

Texas College

University of California, Los Angeles

Colorado State University

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Inoculation of a Poultry Isolate Salmonella enteritidis on Egg Vitelline Membrane: Survival and Growth in Egg Components after Different Refrigeration Storage Times

American Journal of Agricultural and Biological Sciences (2007)

Zoë Howard R.W. Moore I.B. ZABALA DÍAZ W.K. Kim S.G. Birkhold

An in vitro study was designed to determine the extent of Salmonella enterica serovar enteritidis survival and growth permissiveness in egg components isolated from shell eggs held at refrigeration temperature over an 8 week time period. Eggs were collected from a commercial laying facility at one-week intervals for eight weeks and stored at refrigeration temperature. After storage, eggs were dipped in ethanol, cracked aseptically and separated into yolk and albumen samples. S. enteritidis resistant to novobiocin and nalidixic acid were inoculated on to the surface of the yolk membrane at a concentration of approximately 10 6 CFU mL¯ 1 . Yolks were then covered with albumen and incubated for 24 hrs at 25oC. After incubation, eggs were separated into component parts. Samples were removed from yolk, albumen and yolk membrane and diluted 10-fold in sterile phosphate buffered saline. In albumen, S. enteritidis counts were increased in weeks 3 and 8 compared to week 1 (trial 2). The frequency of eggs exhibiting net growth of S. enteritidis in albumen occurred at week 7 versus weeks 0 and 1 in trial 1 and weeks 3 and 8 versus weeks 0 and 2 in trial 2. In the membrane fraction, the frequency of eggs exhibiting net growth of S. enteritidis occurred at weeks 5 and 8 versus week 0 in trial 2. In the yolk fractions, S. enteritidis counts recovered from week 6 eggs were significantly higher (P<0.05) than those of weeks 0, 2, 3 and 7 (trial 2) and the number of detectable S. enteritidis positive eggs were greater in week 8 than week 5 in trial 1. This suggests that egg components recovered from aged eggs stored at refrigeration temperatures infrequently supported S. enteritidis net growth but generally did not inhibit survivability.

Salmonella enteritidis

Vitelline membrane

10.3844/ajabssp.2007.123.129

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Citations (3)

ASSESSMENT OF AN ESCHERICHIA COLI METHIONINE AUXOTROPH GROWTH ASSAY FOR QUANTIFYING CRYSTALLINE METHIONINE SUPPLEMENTED IN POULTRY FEEDS

Journal of Rapid Methods & Automation in Microbiology (2004)

I.B. ZABALA DÍAZ F.O.C. CARREON W. C. Ellis Steven C. Ricke

ABSTRACT Estimating availability of methionine is relevant to feed formulation since diets can be supplemented with crystalline methionine to meet the minimum requirements of rapidly growing birds. Bacterial assays have been developed to measure the bioavailable levels of several essential amino acids in feeds, including methionine. The E. coli methionine auxotroph strain used in this study exhibited a linear extent of growth response to increasing concentrations of methionine added to the minimal test media, in the range of 0 to 4 μg/mL. In addition the growth rates of the E. coli auxotroph were significantly (P < 0.01) different when the methionine concentrations were varied (0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 μg/mL) in minimal media. To assay feeds, feed grade methionine was added to poultry feed mixtures and samples were diluted with M9 media. Using this assay for estimating crystalline methionine added to feed, the extent of growth of the methionine auxotroph was correlated with the levels of crystalline methionine supplemented in the feed (R 2 = 0.9873). For all supplementation levels methionine recovery percentages ranged from 71 to 80% indicating that the bacterial assay response to crystalline methionine was relatively constant in the presence of the feed matrix. The overall results indicate that the rapid detection of crystalline methionine added to feeds is possible using this E. coli methionine auxotroph growth‐based assay.

Auxotrophy

10.1111/j.1745-4581.2004.tb00060.x

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CONSTRUCTION AND GROWTH KINETICS OF A BIOLUMINESCENT METHIONINE AUXOTROPH ESCHERICHIA COLI STRAIN FOR POTENTIAL USE IN A METHIONINE BIOASSAY

Journal of Rapid Methods & Automation in Microbiology (2002)

C.A. Froelich I.B. ZABALA DÍAZ Steven C. Ricke

Methionine is one of the essential and first limiting amino acids in animal nutrition. In this study, an Escherichia coli methionine auxotroph bacterial strain that exhibits a linear growth response to methionine concentrations was transformed with a plasmid containing genes encoding ampicillin resistance and bioluminescence in order to develop a microbiological technique for methionine quantitation. Transformants were selected based on antibiotic resistance and plasmid containing candidates were confirmed by restriction enzyme digestion and gel electrophoresis. To confirm the bioluminescent phenotype, video imaging of the strain using long exposure photography yielded colonies exhibiting bioluminescence. The strain was also tested in the presence of ampicillin supplemented media with increasing methionine concentrations and growth response (measured as optical density, OD), growth rates and methionine affinities were compared before and after transformation. Although the transformed E. coli methionine auxotroph exhibited somewhat different growth kinetic responses than the nontransformed strain, the standard curves used for estimating methionine concentrations were not different. Based on the results in this study the transformed bioluminescent strain could be used as an OD‐based assay if bioluminescence equipment and materials are not available.

Auxotrophy

Strain (injury)

10.1111/j.1745-4581.2002.tb00013.x

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Citations (9)

POTENTIAL RAPID BIOASSAY FOR ALIMET® USING A METHIONINE ESCHERICHIA COLI AUXOTROPH

Journal of Rapid Methods & Automation in Microbiology (2002)

C.A. Froelich I.B. ZABALA DÍAZ Steven C. Ricke

A potential rapid bioassay for methionine hydroxy analog (MHA) feed additive (ALIMET®) was examined using a methionine auxotroph E. coli strain. Bacterial cells were grown in minimal media containing a concentration range of 0 to 26.8 μM of either L‐methionine or MHA as ALIMET®. Increasing either methionine or MHA concentration increased the growth rate of the methionine auxotroph. The estimated substrate affinities for methionine compared to MHA were not significantly different (P > 0.13) and the maximum growth rate estimates were also similar (P > 0.34). Methionine and MHA standard curves yielded linear responses (R 2 = 0.96) to increasing concentrations of the respective substrate. Based on these results it appears that the E. coli methionine auxotroph would have potential utility for further development of a rapid bioassay of ALIMET®.

Auxotrophy

Strain (injury)

10.1111/j.1745-4581.2002.tb00023.x

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Citations (6)

QUANTIFYING METHIONINE WITH A GREEN FLUORESCENT ESCHERICHIA COLI METHIONINE AUXOTROPH

Journal of Rapid Methods & Automation in Microbiology (2005)

C.A. Froelich I.B. ZABALA DÍAZ Vesela I. Chalova W.‐K. Kim Steven C. Ricke

ABSTRACT Methionine is one of the essential and primary limiting amino acids in animal nutrition. In this study, an Escherichia coli methionine auxotroph bacterial strain that exhibited a linear growth response to methionine concentrations was transformed with a plasmid containing genes encoding for a green fluorescent protein, in order to develop a fluorescent bioassay technique for methionine quantitation. Transformants were grown on arabinose‐supplemental media and kept at 27C. The strain was also tested in supplemented media with increasing methionine concentrations, and growth response (measured as optical density [OD]) was compared with fluorescence. The transformed E. coli methionine auxotroph exhibited low OD values, but the OD and fluorescent standard curves used for estimating methionine concentrations were linear with increasing increments of methionine concentration (OD, R 2 = 0.97 and 0.89; fluorescent, R 2 = 0.90 and 0.89) as were the corresponding fluorescent responses (OD versus fluorescent, R 2 = 0.85 and 0.91). The transformed fluorescent strain also responded to enzymatic digests of selected animal feed proteins, yielding differences in available methionine among the different feed protein sources. Using the fluorescence‐based bacterial growth assay to quantify methionine in microtiter plates has potential for assessment of methionine levels in animal feed samples.

Auxotrophy

Strain (injury)

10.1111/j.1745-4581.2005.00017.x

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Citations (5)

In vitro Survival and Growth of Salmonella Typhimurium inoculated on Yolk Membrane after long Term refrigerated Storage of Shell Eggs

Journal of Consumer Protection and Food Safety (2006)

Zoë Howard R.W. Moore I.B. ZABALA DÍAZ W. K. Kim S.G. Birkhold

Yolk

Flock

Vitelline membrane

Salmonella enterica

10.1007/s00003-006-0006-5

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Citations (3)

A bioluminescent Escherichia coli auxotroph for use in an in vitro lysine availability assay

Journal of Microbiological Methods (2000)

A.M. ERICKSON I.B. ZABALA DÍAZ Y.M. KWON Steven C. Ricke

Auxotrophy

10.1016/s0167-7012(00)00121-4

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Citations (24)

GROWTH RESPONSE AND RECOVERY IN SELECTIVE MEDIA OF A LYSINE AUXOTROPH ESCHERICHIA COLI FOR A RAPID MICROBIOLOGICAL ASSAY

Journal of Rapid Methods & Automation in Microbiology (1999)

I.B. ZABALA DÍAZ A.M. ERICKSON Steven C. Ricke

Abstract Human foods and animal feeds vary in their amino acid availability based upon the nature of the protein source and subsequent processing treatments to which the source may have been subjected during manufacture. In this study, growth and recovery of an Escherichia coli lysine auxotroph assay organism was tested in the presence of an antibiotic and antifungal supplemented medium previously developed. Overall growth rate comparisons in amended liquid minimal media showed that addition of antistatic agents did not alter the growth rate of the indicator strain and that it is independent of lysine concentration. Six different animal feeds were studied to determine the potential background contribution of indigenous feed Escherichia coli and whether the selective medium would suppress these organisms. Recovery of the indicator strain used for the rapid bacterial lysine assay was above 94% in all feed suspensions. In addition to this, indigenous microflora of the animal feeds was unable to grow in the presence of the antistatic agents selected. Microbial growth measured as agar plate colonies from short (1 week) and long term storage (6 months) feeds were completely suppressed on the antibiotic supplemented plates after 24 h of incubation. This result confirms that the amendments will suppress the growth of indigenous feed E. coli populations during the time frame typically used to conduct the rapid bacterial lysine assay with the E. coli lysine auxotroph without altering the growth rate response of the auxotroph.

Auxotrophy

Bacterial growth

10.1111/j.1745-4581.1999.tb00398.x

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Citations (8)

ADAPTATION OF A METHIONINE AUXOTROPH ESCHERICHIA COLI GROWTH ASSAY TO MICROTITER PLATES FOR QUANTITATING METHIONINE

Journal of Rapid Methods & Automation in Microbiology (2002)

I.B. ZABALA DÍAZ C.A. Froelich Steven C. Ricke

A rapid microtiter methionine assay was developed using a methionine auxotroph E. coli strain. The bacterial strain was first grown on rich media to promote extensive bacterial growth and the cells were depleted to exhaust all endogenous methionine. After depletion, cells were transferred to minimal media with increasing concentrations of methionine and microtiter plates were incubated at 37C for 6 h. Methionine microtiter standard curves yielded linear growth responses to increasing concentrations of methionine in the range of 0 to 26.8 μM. Addition of different antibiotic and antifungal agents to the media did not significantly alter the linear growth response observed in the microtiter assay. This microtiter plate E. coli methionine assay has potential as a rapid in vitro assay method for quantifying methionine.

Microtiter plate

Auxotrophy

Strain (injury)

10.1111/j.1745-4581.2002.tb00257.x

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Citations (11)

Influence of short chain fatty acids and lysine on Salmonella typhimurium cadA expression

Antonie van Leeuwenhoek (2004)

I.B. ZABALA DÍAZ Steven C. Ricke

10.1023/b:anto.0000020271.11533.71

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Citations (9)