Taxonomy, Role, and Significance of Microorganisms in Foods
23
clostridial species of known importance in foods remain in the genus at this time. The five new genera
appear to be unimportant in foods.
Corynebacterium (co • ry • ne • bac • ter’ • i • um; Gr. coryne, club). This is one of the true coryneform
genera of Gram-positive, rod-shaped bacteria that are sometimes involved in the spoilage of vegetable
and meat products. Most are mesotrophs, although psychrotrophs are known, and one, C. diphtheriae,
causes diphtheria in humans. The genus has been reduced in species with the transfer of some of the
plant pathogens to the genus Clavibacter and others to the genus Curtobacterium. The mol% G + C
content of DNA is 51–63.
Enterobacter (en • te • ro • bac’ter). These enteric Gram-negative bacteria are typical of other Enterobacteriaceae relative to growth requirements, although they are not generally adapted to the gastrointestinal tract. They are further characterized and discussed in Chapter 20. E. agglomerans has been
transferred to the genus Pantoea. E. sakazakii is discussed in Chapter 31.
Enterococcus (en • te • ro • coc’cus). This genus was erected to accommodate some of the Lancefield
serologic group D cocci. It has since been expanded to more than 16 species of Gram-positive ovoid
cells that occur singly, in pairs, or in short chains. They were once in the genus Streptococcus. Some
species do not react with group D antisera. The genus is characterized more thoroughly in Chapter 20,
and its phylogenetic relationship to other lactic acid bacteria can be seen in Figure 25–1.
Erwinia (er • wi’ni • a). These Gram-negative enteric rods are especially associated with plants. At least
three species have been transferred to the genus Pantoea,
33 and the former E. carotovora and E. chrysanthemi are now in the genus Pectobacterium as P. carovovorum and P. chrysanthemi (see Chapter 6).
Escherichia (esch • er • i’chi • a). This is clearly the most widely studied genus of all bacteria. Those
strains that cause foodborne gastroenteritis are discussed in Chapter 27, and E. coli as an indicator of
food safety is discussed in Chapter 20.
Flavobacterium (fla • vo • bac • te’ri • um). These Gram-negative rods are characterized by their production of yellow to red pigments on agar and by their association with plants. Some are mesotrophs,
and others are psychrotrophs, where they participate in the spoilage of refrigerated meats and vegetables. Some of the former flavobacterial species have been placed in the following five new genera:
Empedobacter, Chryseobacterium, Myroides, Sphingomonas, and Sphingobacterium.
Hafnia (haf’ni • a). These Gram-negative enteric rods are important in the spoilage of refrigerated
meat and vegetable products; H. alvei is the only species at this time. It is motile and lysine and
ornithine positive, and it has a mol% G + C content of DNA of 48–49.
Kocuria (Ko • cu’ri • a, after M. Kocur). A new genus split off from the genus Micrococcus.
42 The
three species (K. rosea, K. varians, and K. kristinae) are oxidase negative and catalase positive, and
the mol% G + C content of DNA is 66–75.
Lactobacillus (lac • to • ba • cil’lus). Taxonomic techniques that came into wide use during the 1980s
have been applied to this genus, resulting in some of those in the ninth edition of Bergey’s Manual
being transferred to other genera. Based on 16S rRNA sequence data, three phylogenetically distinct
clusters are revealed,
10 with one cluster encompassing Weissella. In all probability, this genus will
undergo further reclassification. They are Gram-positive, catalase-negative rods that often occur in
23
clostridial species of known importance in foods remain in the genus at this time. The five new genera
appear to be unimportant in foods.
Corynebacterium (co • ry • ne • bac • ter’ • i • um; Gr. coryne, club). This is one of the true coryneform
genera of Gram-positive, rod-shaped bacteria that are sometimes involved in the spoilage of vegetable
and meat products. Most are mesotrophs, although psychrotrophs are known, and one, C. diphtheriae,
causes diphtheria in humans. The genus has been reduced in species with the transfer of some of the
plant pathogens to the genus Clavibacter and others to the genus Curtobacterium. The mol% G + C
content of DNA is 51–63.
Enterobacter (en • te • ro • bac’ter). These enteric Gram-negative bacteria are typical of other Enterobacteriaceae relative to growth requirements, although they are not generally adapted to the gastrointestinal tract. They are further characterized and discussed in Chapter 20. E. agglomerans has been
transferred to the genus Pantoea. E. sakazakii is discussed in Chapter 31.
Enterococcus (en • te • ro • coc’cus). This genus was erected to accommodate some of the Lancefield
serologic group D cocci. It has since been expanded to more than 16 species of Gram-positive ovoid
cells that occur singly, in pairs, or in short chains. They were once in the genus Streptococcus. Some
species do not react with group D antisera. The genus is characterized more thoroughly in Chapter 20,
and its phylogenetic relationship to other lactic acid bacteria can be seen in Figure 25–1.
Erwinia (er • wi’ni • a). These Gram-negative enteric rods are especially associated with plants. At least
three species have been transferred to the genus Pantoea,
33 and the former E. carotovora and E. chrysanthemi are now in the genus Pectobacterium as P. carovovorum and P. chrysanthemi (see Chapter 6).
Escherichia (esch • er • i’chi • a). This is clearly the most widely studied genus of all bacteria. Those
strains that cause foodborne gastroenteritis are discussed in Chapter 27, and E. coli as an indicator of
food safety is discussed in Chapter 20.
Flavobacterium (fla • vo • bac • te’ri • um). These Gram-negative rods are characterized by their production of yellow to red pigments on agar and by their association with plants. Some are mesotrophs,
and others are psychrotrophs, where they participate in the spoilage of refrigerated meats and vegetables. Some of the former flavobacterial species have been placed in the following five new genera:
Empedobacter, Chryseobacterium, Myroides, Sphingomonas, and Sphingobacterium.
Hafnia (haf’ni • a). These Gram-negative enteric rods are important in the spoilage of refrigerated
meat and vegetable products; H. alvei is the only species at this time. It is motile and lysine and
ornithine positive, and it has a mol% G + C content of DNA of 48–49.
Kocuria (Ko • cu’ri • a, after M. Kocur). A new genus split off from the genus Micrococcus.
42 The
three species (K. rosea, K. varians, and K. kristinae) are oxidase negative and catalase positive, and
the mol% G + C content of DNA is 66–75.
Lactobacillus (lac • to • ba • cil’lus). Taxonomic techniques that came into wide use during the 1980s
have been applied to this genus, resulting in some of those in the ninth edition of Bergey’s Manual
being transferred to other genera. Based on 16S rRNA sequence data, three phylogenetically distinct
clusters are revealed,
10 with one cluster encompassing Weissella. In all probability, this genus will
undergo further reclassification. They are Gram-positive, catalase-negative rods that often occur in