Acidovorax Acidovorax is a genus of Proteobacteria. Typically are plant pathogens and infections are extremely rare in humans. Microbiological properties: Straight to slightly curved rods, 0.2–1.2 × 0.8–5.0 µm. Occur singly, in pairs, or in short chains. Gram negative. Motile by means of one or rarely two or three polar flagella. Obligate aerobic Most strains do not produce pigments on nutrient agar, but some phytopathogenic strains may produce a yellow to slightly brown diffusible pigment. Oxidase positive Urease activity varies among strains. Acidovorax strains can be isolated from soil, water, and infected plants.

2. Presented By:
Muneeb Anwer
Topic Of Presentation
Acidovorax

3. Acidovorax

4.  Acidovorax is a genus of Proteobacteria.
 Typically are plant pathogens and infections are
extremely rare in humans.

5.  Straight to slightly curved rods, 0.2–1.2 × 0.8–
5.0 µm.
 Occur singly, in pairs, or in short chains.
 Gram negative.
 Motile by means of one or rarely two or three
polar flagella.
 Obligate aerobic
Microbiological properties

6.  Most strains do not produce pigments on
nutrient agar, but some phytopathogenic
strains may produce a yellow to slightly
brown diffusible pigment.
 Oxidase positive
 Urease activity varies among strains.
 Acidovorax strains can be isolated from soil,
water, and infected plants.

9.  Kingdom: Bacteria
 Phylum: Proteobacteria
 Class: Betaproteobacteria
 Order: Burkholderiales
 Family: Comamonadaceae
 Genus: Acidovorax
Taxonomy

10. Species
 Acidovorax citrulli
 Acidovorax oryzae
 Acidovorax konjaci
 Acidovorax radicis
 Acidovorax facilis
 Acidovorax anthurii
 Acidovorax soli
 Acidovorax cattleyae
 Acidovorax caeni
 Acidovorax temperans
 Acidovorax valerianellae
 Acidovorax wohlfahrtii
 Acidovorax defluvii
 Acidovorax aerodenitrificans

11. Acidovorax citrulli

12.  The bacterium was isolated from water-soaked
lesions on cotyledons of infested watermelon
seedlings in the USA (Webb and Goth, 1965).
 The bacterium was phenotypically similar to
Pseudomonas pseudoalcaligenes but it was differed
from pathogen of watermelon, cucumber and squash
(Schaad et al., 1978).
 Therefore, this new bacterium was named P.
pseudoalcaligenes subsp. citrulli.
Acidovorax citrulli

13.  In 1991 found a close similarity between this
bacterium and Pseudomonas avenae and thus was
renamed P. avenae subsp. citrulli.
 The watermelon bacterium and other subspecies of P.
avenae constitute a separate rRNA branch within the
family Comamonadaceae.
 The rRNA branch to be most closely related to the
genus Acidovorax and the watermelon fruit blotch
bacterium was renamed Acidovorax avenae subsp.
citrulli. Willems et al. (1992)
 The current preferred name for this pathogen is
Acidovorax citrulli.

14. On the basis of carbon source utilization, DNA-
fingerprinting profiles and pathogenicity
A. citrulli is divided into two distinct groups
1. The group I strains are mainly associated with
non-watermelon plants (mainly melon)
2. The group II includes strains that were mainly
isolated from watermelon.
Strains

15.  A. citrulli Strain. M1
 A. citrulli Strain. M2
 A. citrulli Strain. M6
Group I Strains

16.  A. citrulli Strain. W1
 A. citrulli Strain. W2
 A. citrulli Strain. 7a1
 A. citrulli Strain. W4
 A. citrulli Strain. W6
Group II Strains

17. After 4 days of incubation on
media at 27°C colonies are
 1.0–1.5 mm in diameter
 Convex
 Slightly spreading with clear
margins
 Whitish‐grey in colour
Colonies are non-fluorescent on
King's medium B.
Growth On Nutrient Ager

18. Bacterial fruit blotch & seedling
blight of cucurbit plants

19.  Most economically important plant diseases and their
causal agents were described between the late 19th
and early 20th centuries, with the emergence of
modern phytopathology.
 The documented history of BFB began in the 1960s.
 End of the 1980s was the economic impact of this
disease realized.
 In 1965, Webb and Goth reported an unidentified,
seed-borne phyto bacterium, isolated from necrotic
watermelon cotyledons of different plant.
 During the 1990s, the rapid spread.
History

20.  A. citrulli has been distributed throughout the
watermelon growing areas of the USA and in many
other watermelon producing areas of the world.
Distribution

22. Symptoms of the disease can be observed on
 Seedling
 Leaves
 Vines
 Fruits
Symptoms

23.  Seedling symptoms
include water-soaked
lesions on cotyledons
and later become
necrotic
 Seedling collapse and
death
Symptoms on Seedling

24.  Leaf lesions can
spread along the
midrib and main veins.
 Lesions appear dark-
brown to black on
watermelon and light
to reddish-brown on
melon
Symptoms on Leaves

25.  On vines, brown
necrotic
appearance.
 Bacterial ooze may
emerge from
cankers.
Symptoms on vines

26.  A dark, olive-green blotch
on the upper surface of
infected fruit that begins
as a small, water-soaked
area a few millimeters in
diameter and rapidly
enlarges to a lesion
several centimeters in
diameter with irregular
margins.
Symptoms On watermelon Fruits

27.  Initially, the lesions do not
extend into the flesh of
the watermelon.
 In advanced stages of
lesion development, the
initial infection site may
become necrotic.
 Cracks in the skin of fruit
surface may occur,
resulting in fruit rot.

28.  On melon fruits, symptoms
appear as small sunken
lesions (sometimes very
many) which do not expand
on the fruit surface.
 When numerous, such
lesions may fused and cause
large rotting areas and long
cracks on fruits
Symptoms on melon Fruits

29.  Acidovorax citrulli strains
are pathogenic to various
species of the
Cucurbitaceae family,
including watermelon,
melon, squash, pumpkin
and cucumber.
 Significant economic
losses have been reported
in watermelon and melon.
HOST RANGE

30.  Acidovorax citrulli is seed borne and seed transmitted.
 When infested seeds are planted directly into the soil,
the emerging seedlings may shows symptoms by 6 to
10 days after germination.
 High temperatures and Relative Humidity increase
disease incidence.
 Bacterium penetrates through stomata and wounds to
establish infections that result in foliar lesions and
blight.
EPIDEMIOLOGY

32.  Host-Plant Resistance
Triploid watermelons are less susceptible to A. citrulli
than diploid watermelons.
 Cultural Control and Sanitary Methods
1. Decontamination of hands and tools after contact
with plants.
2. Closing sides of the transplant house during storms
or windy periods.
3. Spread of the bacterium in the greenhouse can be
minimized by low humidity, low temperatures, and
bottom watering
Management

33. 4. Decontaminate a transplant house that had infected
seedlings and wait at least 2-3 weeks to plant cucurbits
in it again.
5. A 0.5% sodium hypochlorite solution, as well as
commercial bactericides, may be used for
decontamination.
Chemical Control
Applications of copper-containing bactericides are
reduced the incidence of disease.

34. Biochemical and physiological tests
Tests Result
Gram’s reaction -
Cytochrome c oxidase reaction +
Oxidative +
Fluorescent pigment on King’s B medium
-
Motility +
Gelatin liquefaction
-
Growth at 41°C
+

35.  Formerly known as Acidovorax avenae subsp. avenae
Acidovorax oryzae

36.  Main hosts
 Oryza sativa (rice)
 Saccharum officinarum (sugarcane)
 Sorghum bicolor (sorghum)
 Zea mays (maize)
Host Range

37. Bacterial Leaf Blight

38. Symptoms at the seedling stage were divided into four
types
 Inhibition of germination
 Brown stripes on a leaf
 Curving of a leaf sheath
 Abnormal elongation of a mesocotyl.
After the infected seedlings were transplanted to paddy
fields, the symptoms were masked.
Symptoms on Rice

39.  Water-soaked stripes on
the leaves and leaf sheaths
begin as dark green and
later turn brown.
 On the leaves, stripes occur
along the midrib, leaf
margins.
 Lesions measure up to 10
cm x 1 mm, but they may
fused to form wider
affected areas.
Symptoms on Rice

40.  Bacteria may also attack
young, unfolded leaves
(which may result in
stunting or death of the
seedling) and grain
discoloration may occur
in mature plants.
Symptoms on Rice

41.  Leaf lesions are narrow,
white to straw and initially
appear oil-soaked and
translucent.
 Lesions tend to be restricted
by veins.
 Large, elongate, irregular
spots or bands often
develop from when lesions
fused.
Symptoms On Maize

42.  On leaves long, narrow, uniform,
dark-red stripes.
 The disease occurs mostly on the
young and middle-aged leaves
rather than on the oldest leaves
of the plant.
 The earliest stages of infection
are recognized by the
appearance of watery-green
stripes, usually midway in the
leaf and near.
Symptoms on sugarcane

43.  Stripes spread up and down the leaf,
becoming reddish in colour, and later turning
dark red.
 Stripes vary in width from 0.5 to 4.0 mm, and
in length from a few centimeters to the entire
length of the leaf blade.
 Two or more stripes may fuse to form broad
bands of diseased leaf tissue.
Symptoms on sugarcane

44.  Circular spots with
water-soaked borders
and necrotic centers.
Symptoms on Sorghum

45. Distribution

46.  Cultural Control
 Keep fields clean remove weed hosts and plow under
rice stubble, straw which may be infected by the
bacteria.
 Treat seeds with hot water.
 Use balanced amounts of plant nutrients, especially
nitrogen.
Control for Rice

47.  Plant resistant varieties.
 Chemical Control
A copper-based fungicide applied can be effective in
controlling the disease.

48.  Colony are white, shiny,
round, smooth, convex,
and 1.0 - 1.5 mm in
diameter after 4 days in
the circle that showed
different morphology
with saprophytic.
Growth On Nutrient Ager

49.  ATCC 19882
 CCUG 15836
 CFBP 2426
 CIP 106433
 Dye MS1
 FC-143
 ICMP 3960
 ICPB 30003
 ICPB PS177
 ICPB PSS177
 LMG 10904
 LMG 1806
 NCPPB 1392
Type strain

50.  Acidovorax konjaci is a
 Gram-negative
 Rod-shaped measuring 0.5 x 1.8-2.3 µm
 Motile bacterium with a single polar
flagellum
Acidovorax konjaci

51.  The bacterium was first described in Japan by
Goto as Pseudomonas
pseudoalcaligenes subsp. konjaci.
 The pathogen was transferred by Willems in
1992 to the genus, Acidovorax , and designated
Acidovorax konjaci.
History

52.  Colonies are white, round,
transparent, smooth and
slightly convex on YP agar.
 The colony size is 0.8 to
1.0 mm in diameter at 48
hours on YP agar and 2-3
mm within 5 days at 280C
Growth on Media

53. Causes Leaf Blight konjac

54.  On konjac leaf lesions
begin as small, dark
brown, angular, water-
soaked spots between the
veins.
 Under humid conditions
the lesions fused causing
severe blighting of the
entire leaf.
Symptoms

55.  The bacterium continues
to move down the petiole
and eventually may cause
a soft rot of the roots and
corm.

56.  Acidovorax konjaci was first described in Japan from
leaves konjac (Amorphophallus konjac).
 Subsequent reports have indicated it causes leaf spots
and brown to black discoloration of radish roots in
Korea.
 It has been identified causing leaf spots and rapid
blighting of petunia cuttings and seedlings and leaf
spots on verbena in commercial greenhouse
production in the US.
 The full distribution has not been documented but it is
suspected to appear sporadically in the greenhouse
trade.
Distribution

57. konjac

58.  Management of diseases caused by Acidovorax
konjaci is largely dependent on prevention by
good sanitation.
 The pathogen has not been documented to be
disseminated by seed however, long distance
spread is likely by trade in contaminated
propagation material in production of
greenhouse ornamentals.
 Decontaminated pots, tools or handling.
Management

59. Chemical Control:
 Copper based compounds may help reduce spreading
of disease.

60.  Causes brown
spots on orchids.
Acidovorax cattleyae

61.  This pathogen was first described Italy (1911)
as Pseudomonas cattleyae
 Re-classified as A. avenae subsp. cattleyae
(1992)
 Finally as A. cattleyae (2008).
 Infections by this bacterium have been
recorded from Australia, Italy, the
Netherlands, Philippines, Taiwan and the USA.
History

62.  Initially, small water-
soaked spots occurred on
seven-month-old leaves.
 Over time, became larger
and brownish and
surrounded by a yellow
halo.
 In the final stage, total
collapse and death of the
whole plant was observed.
Symptoms

63.  Isolated from the surface of wheat-roots.
 In opposite to other Acidovorax-species it has
no phytopathogenic potential.
 Shown that it promote plants growing activity
Acidovorax radicis

64.  DSM 23535
 LMG 25767
 N35
Strain

65.  Acidovorax facilis is an aerobic
 Chemoorganotrophic bacterium
 Used as a soil inoculant in agriculture and
horticulture.
Acidovorax facilis

66.  Members of A. facilis are generally 1.0-5.0 μm long and
0.2-0.7 μm wide.
 Under a microscope, they appear as straight to
slightly curved rods that occurs singly or in short
chains.
 A. facilis are motile via a single flagellum at one end of
the bacterium.
 They are negative by Gram stain and positive by the
oxidase test.
 When grown on nutrient agar, they form
unpigmented colonies.
Description

67.  A. facilis was originally isolated from lawn soil in the
United States by Albert Schatz and Carlton Bovell in
1950 and named Hydrogenomas facilis.
 In 1969, the genus Hydrogenomonas was abandoned
and H. facilis was transferred to the genus
Pseudomonas.
 Pseudomonas was determined to contain several
genera of bacteria
 In 1990 they were transferred to the new genus
Acidovorax
History

68.  A. facilis has been used in agriculture and horticulture
as a soil additive to improve plant growth.
 A nitrilase enzyme from A. facilis has been
engineered into E. coli for the commercial production
of 3-hydroxyvaleric acid.
Uses