This document provides information on the classification and characteristics of microorganisms important in food bacteriology. It discusses the morphological, cultural, and physiological characteristics used to classify bacteria. Key points:
- Morphological characteristics include shape, structure, staining, and presence of spores, flagella, or capsules.
- Cultural characteristics refer to a bacteria's appearance and growth patterns on agar plates and in broth, such as colony shape, pigmentation, and turbidity in broth.
- Physiological characteristics involve a bacteria's metabolic activities, like fermentation of carbohydrates and production of acids or gases.
- Several genera of bacteria important in food are described, including Bacillus, Clostridium, E.
2. Bacteria
SYLLABUS
ďą Morphological characteristics important in Food Bacteriology
ďą Cultural and Physiological characteristics important in Food
Bacteriology
ďą Genera of bacteria important in Food Bacteriology groups
5. Prokaryotes Vs Eukaryotes
Character Prokaryotes Eukaryotes
Nucleus
Nuclear
membrane
Absent Present
Nucleolus Absent Present
Chromosome One circular One or more paired and
linear
Cell division Binary fission Mitosis
Cytoplasmic
membrane
Structure and
Composition
fluid phospholipid bilayer,
lacks sterols
fluid phospholipid bilayer
containing sterols
Function Incapable of endocytosis
(phagocytosis and
pinocytosis) and
exocytosis
Capable of endocytosis
and exocytosis
6. Nucleolus
⢠It is the largest structure in the nucleus of eukaryotic cell, where it primarily
serves as the site of ribosome synthesis
7. Endocytosis
It is a form of active transport in which a cell transports molecules (such as proteins)
into the cell (endo- + cytosis) by engulfing them in
8. Endoplasmic Reticulum
⢠The endoplasmic reticulum is an organelle in
the eukaryotic cells that forms an interconnected
network of tube-like structures known as cisternae
⢠Two types
⢠rough ER: is studded with ribosomes that are the sites
of protein synthesis
⢠Smooth ER: lacks ribosomes and functions
in lipid manufacture and metabolism, the production
of steroid hormones, and detoxification
9. Golgi apparatus
⢠The Golgi apparatus is a major collection and dispatch station of protein products
received from the ER
10. A) Pinocytosis: the ingestion of liquid
into a cell by the budding of small
vesicles from the cell membrane.
B) Phagocytosis: the ingestion of solid into a
cell by the budding of small vesicles from the
cell membrane
11. Sterols
They occur naturally in plants, animals, and fungi, with the most familiar type of animal
sterol being cholesterol
14. Morphology: Shape of Bacteria
1. Coccus (Cocci): bacterium that has a spherical, ovoid, or generally round shape
15. Bacteria- Cocci
B) Diplococci
⢠pairs of cocci
⢠Example: Streptococcus pneumoniae
C) Streptococci
⢠chains of cocci
⢠e.g. Streptococcus pyogenes
16. D) Staphylococci
⢠Irregular (grape-like) clusters of cocci
⢠e.g. Staphylococcus aureus
E) Tetrads
⢠Clusters of four cocci arranged within
the same plane
⢠e.g. Micrococcus
Bacteria- Cocci
18. Shape- Bacilus
⢠Rod-shaped bacteria
⢠On the basis of arrangement of organisms, they can be described as
A) Bacillus: The rod-shaped bacteria cells, are present as single individuals.
19. B) Diplobacilli:
⢠Two bacilli arranged side by side with
each other
C) Streptobacilli:
⢠Bacilli arranged in chains
Shape- Bacilus
20. D) Vibrios:
⢠They are comma-shaped bacteria
⢠e.g. Vibrio cholarae
E) Spiral:
⢠Spiral shape
⢠Eg. Spirillus
Shape- Bacilus
21. Pleomorphic Bacteria
⢠These bacteria lack in rigid cell wall
⢠Highly pleomorphic and of indefinite shape
⢠They occur in round or oval bodies and in interlacing
filaments
⢠Eg. Mycoplasmas
23. Basis-Presence of Flagella
A. Monotrichous e.g Pseudomona auregenosa
B. Amphitrichous
C. Lophotrichous e.g Pseudomona flouresence
D. Peritrichous e.g Salmonella typhi
E. Atrichous e.g spirochas
24. Arrangement of Flagella
A) Monotrichous
⢠single flagellum at one pole
⢠e.g Pseudomona auregenosa
B) Amphitrichous
⢠flagella at both poles
⢠Eg. Alkaligens faecalis.
25. C) Lophotrichous
⢠Tuft of flagella at one end
⢠e.g Pseudomona flouresence
D) Peritrichous â
⢠flagella all over
⢠e.g Salmonella typhi
Arrangement of Flagella
27. On the basis of Staining
⢠Gram positive
⢠Gram Negative
28. Gram Staining
⢠Gram staining is a method of staining used to
differentiate bacterial species into two large groups
⢠Differential Technique
⢠Technique by Danish bacteriologist- Hans Christian Gram
Gram-positive Gram-positive
33. 1. Crystal Violet:
2. Gramâs Iodine
⢠First of all microbial smear is treated with crystal violet dye
⢠It stains all microorganism purple
⢠Mordant Gramâs Iodine is added
⢠It acts as a stabilizer that causes the dye to form large
complexes in the peptidoglycan layer of the cell wall
⢠The thicker Gram positive cell wall peptidoglycan is able to
trap more firmly the large complex than those of Gram
negative cell
Gram Staining
34. 3. Alcohol:
4. Safranin:
Addition of alcohol dissolve the lipid in the outer layer and
removes the dye from peptidoglycan layer- only in case of G
(-) bacteria
After alcohol treatment, Gram negative bacteria are
colourless, counterstain safranin stains them pink
Gram Staining
35. Encapsulation
Capsule: It is a polysaccharide layer that lies outside the cell wall
sticky capsule helps the bacterium to adhere to the cell surfaces
inside the host tissues.
Capsules also contain water which protects the bacteria
against desiccation
It enhances the ability of bacteria to cause disease
36. Capsule
⢠Gram Positive - immediately exterior to the
murein peptidoglycan layer
⢠Gram Negative- outer membrane
(Lipopolysaccharide layer )
⢠A
39. Endospores
⢠An endospore is a dormant, tough, and non-reproductive
structure produced by certain bacteria
⢠Endospores are formed at an intracellular site, are very
refractile, and are resistant to
⢠heat
⢠ultraviolet light
⢠desiccation
40.
41. Cultural Characteristic of Bacteria
⢠When grown on a variety of media, microorganisms will exhibit visible physical
differences in appearance in their isolated colonies and their growth
⢠These differences are called cultural characteristics or morphology
⢠Significance: may be used as an aid in identifying and classifying some organisms
42.
43. Cultural characteristics
⢠Cultural characteristics or morphology are determined by culturing
microorganisms in nutrient broth and on nutrient agar plates and slants.
⢠After incubation, the characteristics are observed.
48. ⢠After incubation, in a nutrient broth, bacteria may exhibit a particular form
of growth
⢠Turbidity: In a liquid media, some bacteria grow diffusely causing a uniform
clouding of the media
⢠Pellicle: Layering of growth or accumulation of cells at the top
⢠Sediment: accumulation of cells at the bottom of the broth tells something about
the microorganismâs oxygen requirements
⢠Flocculent: Bacterial aggregations are formed and the bacterial growth appears
as small puff balls floating in the broth
⢠Observation of such factors also helps in recognizing types of bacteria.
Cultural Characteristics in Broth media
50. The basic categories of bacterial colony appearance, forms and characteristics on solid
media include:
A)Colony form (shape): Colony shape may be described as
⢠Circular
⢠Irregular
⢠punctiform (tiny)
B) margin (edge):The margin may be
⢠entire (smooth with no irregularities)
⢠undulate (wavy)
⢠lobate (lobed)
⢠Filamentous
⢠rhizoid (branched like roots)
Cultural Characteristics on Solid media
51. Cultural Characteristics
⢠C) Elevation: Colony elevations include
⢠Flat
⢠Raised
⢠Convex
⢠pulvinate (very convex), and
⢠umbonate (raised in the centre)
52. Cultural Characteristics
D) pigmentation (colour)
⢠Pigment production may be
influenced by environmental factors
such as temperature and nutrient
supply
⢠Colony color may be combined with
optical properties such as opaque,
translucent, shiny, or dull
E) Texture: Colony texture may be
⢠Moist
⢠Mucoid
⢠dry
53. Pigmented Bacteria
Pigments Microorganism
Violet Chromobacterium violacein
Yellow Xanthomonas campestris
Orange Sarcina
Red Serratia marcescens
Brown Rhizobium
Golden Staphylococcus aureus
White Staphylococcus epidermis
Pink Micrococcus roseus
54. Protein 1 Polypeptide Peptide
Amino
Acid
1- Proteinase
2- Peptidase
3. Peptidase
2 3
Physiological characteristic of Bacteria
59. Genus Acetobacter
⢠Acetic acid bacteria are characterized by the
ability to convert ethanol to acetic acid in the
presence of oxygen
⢠Acetobacter
⢠rod-shaped
⢠motile
⢠Source: fruits, vegetables, souring fruits, and
alcoholic beverages.
⢠Causes spoilage in alcoholic beverages
60. Genus Alcaligenes
Alkaline reaction is
produced in the
medium of growth
A. viscolactis. causes ropiness in milk, and
A. metalcaligenes gives a slimy growth on cottage cheese.
Source
ďś Manure
ďś Feeds
ďś soil
ďś Water
61. The endospores are aerobic to facultative may be
⢠mesophilic (B. subtilis)
⢠thermophilic (B. stearothermophilus)
⢠actively proteolytic ( sweet-curdle milk; B. cereus )
⢠moderately proteolytic, or non proteolytic
⢠gas-forming or not
⢠lipolytic or not
Genus Bacillus (Gram Positive)
Source: Soil
62. Genus Clostridium (Gram Positive)
⢠Endospores: anaerobic to microaerophilic
⢠swell the end or middle of the rods
⢠mesophilic(C perfringens - "stormy
fermentation" of milk, Clostridium butyricum)
⢠thermophilic (Clostridium thermosaccharolyticum)
64. Genus E coli (Gram Negative)
⢠Gram-negative
⢠non-spore forming,
⢠facultative anaerobic
⢠rod-shaped
⢠Source:
⢠Water
⢠Intestinal tract of warm
blooded organism
⢠Sewage
65. Genus Lactobacillus (Gram positive)
Heterofermentative
⢠They ferment sugar to lactic acid,
alcohol, other acid
⢠Hetero-fermentative species
growing at
ď higher temperatures
ďź L. delbrueckii.
ďź L. fermentum
ď lower temperatures are
ďź L. brevis
ďź L. buchneri
ďź L. pastorianus
Homofermentative
⢠They ferment sugar chiefly to lactic
acid
⢠optimal temperatures of 37 C or
above include
ďź L. bulgaricus
ďź L. lactis
ďź L. acidophilus
ďź L.thermophilus.
⢠lower optimal temperatures include
ďź L. casei
ďź L. plantarum
ďź L. leichmannii
66. ⢠Heterofermentative
⢠Convert sugar to lactic acid plus acetic acid, ethyl alcohol, and
carbon dioxide
⢠generally slime-forming
⢠catalase-negative ???
Genus Leuconostoc (Gram positive)
Citric acid
Diacetyl
L. dextranicum and
L. cremoris
67. Genus Leuconostoc (Gram positive)
⢠ovoid cocci
⢠form chains
⢠Habitat - surface of plants
68. Genus Streptococcus (Gram positive)
⢠pairs, chains
⢠all Homofermentative
⢠catalase-negative
⢠Groups:
1. pyogenic
2. viridans
3. lactic
4. enterococcus groups
69. The pyogenic
⢠pus-producing group pathogenic streptococci
⢠S. agalactiae- mastitis in cows (fatal mammary
gland infection)
⢠S. pyogenes-human septic sore throat, scarlet fever,
and
⢠The pyogenic streptococci cannot grow at 10 or
450C
70. The viridans
⢠It includes S. thermophilus S. bovis
⢠it is thermoduric
⢠these species can grow at 450C but not at
100C
71. The lactic
⢠group contains the important dairy bacteria, S. lactis and S.
cremoris*
⢠grow at 100C but not at 450C
⢠These bacteria are used as starters for cheese, cultured buttermilk,
butter, along with Leuconostoc spp., and
⢠S. lactis often is concerned in the souring of raw milk.
72. The enterococci
⢠consists of S. faecalis and S. faecium
⢠S.faecalis is usually the more heat-resistant and
comes more from human sources
⢠whereas S. faecium come from plant source
⢠Bacteria of this group can grow at both 10 0C and
45 0C.
74. Saccharolytic bacteria
⢠Disaccharides /polysaccharides sugars.
⢠Amylolytic bacteria possess amylase to bring about the
hydrolysis of starch outside the cell.
⢠Amylolytic bacteria
ďźBacillus subtilis
ďźClostridium butyricum
75. Lactic acid bacteria or lactics
⢠These bacteria ferment sugars to lactic acid.
⢠desirable in making products such as sauerkraut and cheese.
⢠undesirable in terms of spoilage of wines because they usually form acid
rapidly.
⢠Example:
ďźLeuconostoc
ďźLacto bacillus
ďźStreptococcus
ďźPediococcus.