The Isolation and Characterization of the Tribe Mimeae in Foodstuffs

The availability of a strain of Acinetobacter competent for transformation has made it possible to demonstrate the genetic relatedness of a large variety of gram-negative, oxidase-negative, nonmotile, and aerobic coccobacilli originally classified into eleven different genera. Deoxyribonucleic acid (DNA) species from 265 such strains are capable of transforming stable auxotrophs of the competent Acinetobacter to prototrophy. The compositions of these DNA species vary from 40 to 46.8% guanine plus cytosine. Strains with widely differing phenotypic properties are also included in this collection of acinetobacters. DNA species from all oxidase-positive strains of Moraxella and from a variety of common bacteria are unable fo transform the competent Acinetobacter. Although acinetobacters are usually considered to be unable to reduce nitrate to nitrite, six strains known to carry out this reduction have been shown to be authentic acinetobacters since their DNA species readily transform the competent Acinetobacter auxotrophs to prototrophy. In contrast to previous findings that acinetobacters rarely grow with glucose as a sole carbon source, the results of the present study show that 17 of the 265 strains grow readily in a glucosemineral medium, and 48 other strains can mutate spontaneously to grow in such a medium. A second competent strain of Acinetobacter, originally unable to use glucose, D-xylose, or D-ribose as carbon sources, has been transformed for ability to dissimilate these compounds using DNA species from strains that normally grow on these sugars. Although most of the 265 Acinetobacter strains studied were originally grown on complex media when isolated from human sources, only nine of these strains require growth factors in order to grow in a mineral medium containing a single carbon and energy source. A simple transformation assay has been devised for rapid examination of large numbers of strains to determine whether or not they are acinetobacters. This assay, which is suitable for routine diagnostic work, includes a procedure for preparation of crude transforming DNA from a small quantity of bacterial paste. Samples of DNA prepared from Acinetobacter cultures that had died on slants and plates were still able to effect transformation of the competent auxotrophs to prototrophy.

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“…the surfaces of various semisolid media. They have also been found to be present in a variety of food products (52).…”

Section: Resultsmentioning

confidence: 99%

“…Some of these organisms appear to be responsible for spontaneous abortion in many different kinds of animals (11). Acinetobacter species have also been isolated from a variety of foods (36,52,54).…”

Section: Discussionmentioning

confidence: 99%

Interspecies Transformation of Acinetobacter : Genetic Evidence for a Ubiquitous Genus

1972

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“…Research reported under project no. 16-23. shown to be widespread, occurring in various types of unprocessed foods, e.g., dairy products (6), fish (9), and vegetables (10).…”

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confidence: 99%

Characterization of Radiation-Resistant Vegetative Bacteria in Beef1

Welch

Maxcy

1975

Applied Microbiology

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Ground beef contains numerous microorganisms of various types. The commonly recognized bacteria are associated with current problems of spoilage. Irradiation, however, contributes a new factor through selective destruction of the microflora. The residual microorganisms surviving a nonsterilizing dose are predominantly gram-negative coccobacilli. Various classifications have been given, e.g., Moraxella, Acinetobacter, Achromobacter, etc. For a more detailed study of these radiation-resistant bacteria occurring in ground beef, an enrichment procedure was used for isolation. By means of morphological and biochemical tests, most of the isolates were found to be Moraxella, based on current classifications. The range of growth temperatures was from 2 to 50 C. These bacteria were relatively heat sensitive, e.g., D10 of 5.4 min at 70 C or less. The radiation resistance ranged from Do values of 273 to 2,039 krad. Thus, some were more resistant than any presently recognized spores. A reference culture of Moraxella osloensis was irradiated under conditions comparable to the enrichment procedure used with the ground beef. The only apparent changes were in morphology and penicillin sensitivity. However, after a few subcultures these bacteria reverted to the characteristics of the parent strain. Thus, it is apparent that these isolates are a part of the normal flora of ground beef and not aberrant forms arising from the irradiation procedure. The significance, if any, of these bacteria is not presently recognized.

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“…nov. have' no presently recognized public health significance (Lewis, 197 1;Thornley, 1963). M-A have been found in a variety of food products (Koburger, 1964;Shewan, 197 1;Snodgrass and Koburger, 1967) without being associated with spoilage, except in marine fish and shellfish (Herbert et al,197 1). However, M-A have been associated with both human and animal infections (Henriksen, 1973).…”

Section: Introductionmentioning

confidence: 99%

EFFECT OF SELECTED SOLUTES ON GROWTH AND RECOVERY OF A RADIATION‐RESISTANT Moraxella SP.

Bruns

Maxcy

1978

Journal of Food Science

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A highly radiation‐resistant Moraxella sp. from beef was more resistant to gamma radiation in frozen beef than Clostridium botulinum 33A spores. Even though the Moraxella sp. was extremely radiation‐resistant, its recovery after irradiation was markedly influenced by the plating medium. Fewer colony‐forming units were recovered in Tryptic Soy Agar (TSA) than in Plate Count Agar (PCA), and differences in recovery became more pronounced with increasing radiation dose. Growth studies of the nonirradiated Moraxella sp. suggested the presence of dialyzable inhibitory factor(s) in Trypticase Soy Broth (TSB) and TSA. The low (0.5%) concentration of NaCl in TSA was shown to be mainly responsible for the slow growth and reduced recovery after irradiation. Reduced recovery was also obtained by plating the Moraxella sp. in PCA plus 0.5% NaCl or PCA plus 6% glucose after irradiation. It was noted that 2 other highly radiation‐resistant isolates identified as Moraxella sp. gave similar results. Sensitivity to low solute concentrations, therefore, appeared to be a general phenomenon for this group.

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The Isolation and Characterization of the Tribe Mimeae in Foodstuffs

Cited by 11 publications

References 18 publications

Interspecies Transformation of Acinetobacter : Genetic Evidence for a Ubiquitous Genus

Interspecies Transformation of Acinetobacter : Genetic Evidence for a Ubiquitous Genus

Characterization of Radiation-Resistant Vegetative Bacteria in Beef1

EFFECT OF SELECTED SOLUTES ON GROWTH AND RECOVERY OF A RADIATION‐RESISTANT Moraxella SP.

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