1. Vibrionaceae

2.  Three members pathogenic to human, other species are
pathogenic for animal and insects.
 The genus Vibrio consists of Gram negative straight or
curved rods, motile by mean of single polar flagellum.
 Most common in surface of waters. Occur in both marine
and freshwater habitat.
 Most disease causing strains are associated with
gastroenteritis but can also infect open wounds and cause
septicemia.

3.  Found in fresh and brackish (slighly salt) water, shellfish and
other seafood
 Major reservoir is not known. Long assumed to be human but
some evidence suggests that it is the aquatic environment.
 Factor of transmission –through water or food. Eg: inadequate
sanitation, lack of person and food hygiene, use a polluted water
to prepare food, inadequate cooked shellfish etc

4.  Cause Cholera (Asiatic cholera or epidermic cholera).
 Causing watery diarrhoea producing ‘rice water’ stool
containing vibrios, epithelial cells and mucus.
 Produce enterotoxin (exotoxin) that activates enzyme
adenylate cyclase
 Adherence factor – motility and extracellular enzymes such
as proteases
 Acute cholera – rapid loss of fluid and electrolytes in stool,
vomit leads to muscular cramps and severe dehydration
(fatal), acidosis, blood urea increase, urine increase in
albumin

5.  Curved rods with rounded ends
 3 x 0.5µm
 Gram negative
 Actively motile with single polar flagellum. To- and fro-
movement (dark-field micsroscopy)
 Non-capsulated, Non-sporing
 Some strain is pleomorphic and lateral flagellum
 Facultative anaerobic rods

6.  Aerobic
 Wide temperature. Optimum 37oC
 Grow in ordinary media but sensitive to acid pH (alkaline;
8.2)
 2-3 mm in size after 18 – 24 hr incubation in optimum
temp.
 Low convex with an entire edge, whitish and translucent
 Older colonies develop a light ochre tinta tube of peptone
water with a flake of mucus from stool and incubating for
only 6 – 8 hrs

7.  Ferment glucose, sucrose, mannitol and maltose without gas
production
 Does not utilise lactose or dulcitol
 Positive in indole and nitrites test
 Non-hemolytic in sheep blood agar (Greig test)
 Can be tested in H2SO4

8.  Recognize the serotypes – Inaba and Ogawa

9.  Hemolysis effect in Greig test
 Resistant to Mukerjee’s V.cholerae group IV phage
 Resistance to polymyxin B, but V.cholerae sensitive to it

10.  Halophilic (salt-loving) vibrio
 Growth best in 2-4% NaCl culture media
 V.cholerae and V.el tor produce large yellow sucrose-
fermenting colonies in thiosulphate bile sucrose (TCBS)
 V.parahaemolyticus colonies are blue-green in TCBS medium

12.  Both are soil bacteria
 Azotobacter and Rhizobiaceae bacterial species are nitrogen
fixers
 Azotobacter is a free-living bacteria
 Rhizobium basically in soil
 Most bacteria in soil are about one micron in length or
diameter.
 Their size varies with their environment.
 Bacteria in -high levels of nutrients ,larger than those in
nutrient- poor .

14.  The majority of bacteria in soil usually occur as single cells.
 Bacteria sometimes join together in chains or clusters. They
mainly have one of two shapes - spheres (called cocci) and
rods (called bacilli).
 Other bacteria have more varied shapes including spirals and
long thin hyphae (although these are less common).

15.  These bacteria take nitrogen from the air (which plants
cannot use) and convert it into a form of nitrogen called
ammonium (NH4+), which plants can use.
 The nitrogenase enzyme controls the process, called
nitrogen fixation, and these bacteria are often called
"nitrogen fixers".

16. It converts atmospheric nitrogen into ammonium, but in the
condition of :
 An easily degradable carbon source is available
 Any nitrogen compounds such as ammonium or nitrate, are
not already present in substantial concentrations
 Soil pH levels are between 6 and 9
 High levels of phosphorus are present
 Very low levels of oxygen are present

17.  These are primarily used to enhance the growth of several
species of plants and crops.
 A correct proportion of bacterial growth could ensure a
high quality of biofertilizer.
 Its capability in maintaining the pH, safe to use and
compatible as chemical fertilizer

18.  Rhizobium is primarily a gram negative, motile, non-sporulating
rod that requires a plant host.
 Species under this genus:
1. R. phaseoli
2. R. leguminosarum
3. R. trifolii
 Other genus are cowpeas Rhizobium and Bradyrhizobium

19.  Rhizobia belong to a specific group of bacteria that form a
mutually beneficial association, or symbiosis, with legume
plants.
 Rhizobia are found in soils of many natural ecosystems. They
may also be present in agricultural areas where they are
associated with both crop legumes (like soybean) and
pasture legumes (like clover).
 Usually, the rhizobia in agricultural areas have been
introduced at sowing by applying an inoculum to the
exterior of the seeds as liquid formations or pellets.