Effect of pH values on the growth of Fusarium species
Abstract
There was narrow range of
pH values used (4.5 to 9.0). With each value three trails were exerted and also
with each trail three replicates (plates) were performed. Thereby, the mean was
calculated for each replicate at each trail from 1st to 7th
day. Also, the total mean for all trails at all days was calculated which in
turn indicates the highest fungal growth at each pH value and incubation period
(days). The results were taken daily from first to seventh day where the
diameter of fungal mat was measured by centimeters. According to the results
which illustrate in table number 1 the best pH value for Fusarium sp growth is
4.5 due to preferable acidity of fungi. At all values of pH no any growth at
first and second days but the growth begins from third day. The best day for
fungal growth at all pH values is 7th day.
Key words
Optimizations;
Fungal growth; Acidity, Alkalinity and PDA
Introduction
A few studies concerning
fungal growth have dealt with the predictive modeling approach (Vali´k et al.
1999 and Panagou et al. 2003). Several factors act on the growth of Fusarium
such as the pH values (Bekada et al. 2004). One of the most influential
factors affecting the fungal community in soil is pH. pH strongly influences abiotic
factors, such as carbon availability (Andersson et al. 2000 and Kemmitt et
al. 2006). In addition, soil pH may control biotic factors, such as the
biomass composition of fungi (Fierer et al. 2006), in both forest (Bååth
et al. 2003; Blagodatskaya and T.-H. Anderson 1998 and Frostegård et
al. 1993), and agricultural soils (Arao, 1999 and Bardgett et al.
2001). Our aim was to assess the fungal growth was affected by medium pH.
Materials and Methods
Fungal Isolate
The isolate of Fusarium
sp was used as test microorganism.
Inoculum preparation
The isolate of Fusarium
sp was grown on Potato Dextrose Agar medium for 7 days at 28 ± 0.5°C to obtain
heavily sporulating cultures.
Growth medium
The
standard growth medium used in the experiment was Potato Dextrose Agar (Difco) for
two purposes Fusarium sp cultivation and measurement of its growth.
Measurement
The
diameters (y, expressed in mm) of the colonies were measured in horizontal
directions daily, at the same time (t, expressed in days) (Gervais et al.
1988).
Different pH values
After preparation and
distribution of Potato Dextrose Agar medium in various conical flasks each of
which has definite pH value which was adjusted by 0.1N HCl and 0.5M NaOH for
acidity and alkalinity adjustment respectively.
Results
This study was begun with
using Fusarium sp for studying the effect of different pH values on its
growth and this fungus is illustrated as shown in figure 1. In this experiment
there was narrow range of pH values used (4.5 to 9.0). With each value three
trails were exerted and also with each trail three replicates (plates) were
performed. Thereby, the mean was calculated for each replicate at each trail
from 1st to 7th day. Also, the total mean for all trails
at all days was calculated which in turn indicates the highest fungal growth at
each pH value and incubation period (days). The results were taken daily from
first to seventh day where the diameter of Fusarium sp mat was measured
by centimeters. According to the results which illustrate in table number 1 the
best pH value for Fusarium sp growth is 4.5 due to preferable acidity of fungi.
At all values of pH no any growth at first and second days but the growth
begins from third day. The best day for fungal growth at all pH values is 7th
day.
Fig. 1: Culture of Fusarium sp (14 Xg)
Table 1: Influence of different pH values on the growth of Fusarium
sp
|
pH value
|
Trails
|
Replicates
(plates)
|
Measurement of Fusarium sp mat diameter (cm)
/ day
|
||||||
|
1st
|
2nd
|
3rd
|
4th
|
5th
|
6th
|
7th
|
|||
|
4.5
|
First
|
I
|
0.0
|
0.0
|
3.0
|
4.1
|
5.0
|
5.7
|
7.4
|
|
II
|
0.0
|
0.0
|
3.2
|
4.3
|
5.3
|
5.9
|
7.8
|
||
|
III
|
0.0
|
0.0
|
3.5
|
4.6
|
5.5
|
6.2
|
8.0
|
||
|
Mean
|
0.0
|
0.0
|
3.2
|
4.3
|
5.2
|
5.9
|
7.7
|
||
|
Second
|
I
|
0.0
|
0.0
|
3.1
|
4.0
|
4.8
|
6.2
|
8.1
|
|
|
II
|
0.0
|
0.0
|
3.4
|
4.2
|
5.2
|
6.0
|
7.8
|
||
|
III
|
0.0
|
0.0
|
3.3
|
4.4
|
5.5
|
6.1
|
8.0
|
||
|
Mean
|
0.0
|
0.0
|
3.2
|
4.2
|
5.1
|
6.1
|
7.9
|
||
|
Third
|
I
|
0.0
|
0.0
|
3.0
|
4.2
|
5.2
|
5.8
|
7.9
|
|
|
II
|
0.0
|
0.0
|
2.8
|
4.2
|
5.2
|
6.3
|
8.4
|
||
|
III
|
0.0
|
0.0
|
3.4
|
4.5
|
5.4
|
6.5
|
8.6
|
||
|
Mean
|
0.0
|
0.0
|
3.0
|
4.3
|
5.2
|
6.2
|
8.3
|
||
|
TOTAL MEAN
|
0.0
|
0.0
|
3.1
|
4.2
|
5.1
|
6.0
|
8.0
|
||
|
6.0
|
First
|
I
|
0.0
|
0.0
|
2.5
|
3.7
|
4.5
|
5.3
|
6.5
|
|
II
|
0.0
|
0.0
|
2.2
|
4.0
|
4.7
|
5.5
|
7.0
|
||
|
III
|
0.0
|
0.0
|
2.2
|
4.2
|
5.2
|
5.9
|
7.4
|
||
|
Mean
|
0.0
|
0.0
|
2.3
|
4.0
|
4.8
|
5.5
|
7.0
|
||
|
Second
|
I
|
0.0
|
0.0
|
2.4
|
4.0
|
4.3
|
5.5
|
7.5
|
|
|
II
|
0.0
|
0.0
|
2.7
|
4.2
|
4.5
|
5.8
|
7.9
|
||
|
III
|
0.0
|
0.0
|
2.2
|
4.5
|
4.5
|
6.0
|
8.2
|
||
|
Mean
|
0.0
|
0.0
|
2.4
|
4.2
|
4.4
|
5.7
|
7.8
|
||
|
Third
|
I
|
0.0
|
0.0
|
2.5
|
4.0
|
4.7
|
5.7
|
8.0
|
|
|
II
|
0.0
|
0.0
|
2.5
|
4.3
|
4.3
|
5.7
|
8.2
|
||
|
III
|
0.0
|
0.0
|
2.3
|
4.3
|
4.5
|
6.1
|
8.5
|
||
|
Mean
|
0.0
|
0.0
|
2.4
|
4.2
|
4.5
|
5.8
|
8.2
|
||
|
TOTAL MEAN
|
0.0
|
0.0
|
2.3
|
4.1
|
4.5
|
5.6
|
7.6
|
||
|
7.5
|
First
|
I
|
0.0
|
0.0
|
0.0
|
2.8
|
3.5
|
5.1
|
6.2
|
|
II
|
0.0
|
0.0
|
0.0
|
2.5
|
4.0
|
5.5
|
6.5
|
||
|
III
|
0.0
|
0.0
|
0.0
|
3.0
|
4.3
|
5.7
|
6.0
|
||
|
Mean
|
0.0
|
0.0
|
0.0
|
2.7
|
3.9
|
5.4
|
6.2
|
||
|
Second
|
I
|
0.0
|
0.0
|
0.0
|
2.6
|
4.1
|
5.5
|
6.7
|
|
|
II
|
0.0
|
0.0
|
0.0
|
2.9
|
4.4
|
5.3
|
6.9
|
||
|
III
|
0.0
|
0.0
|
0.0
|
3.2
|
4.5
|
5.7
|
7.2
|
||
|
Mean
|
0.0
|
0.0
|
0.0
|
2.9
|
4.3
|
5.5
|
7.0
|
||
|
Third
|
I
|
0.0
|
0.0
|
0.0
|
3.0
|
3.9
|
4.1
|
7.0
|
|
|
II
|
0.0
|
0.0
|
0.0
|
2.8
|
4.4
|
4.5
|
7.4
|
||
|
III
|
0.0
|
0.0
|
0.0
|
3.4
|
4.2
|
4.8
|
6.8
|
||
|
Mean
|
0.0
|
0.0
|
0.0
|
3.0
|
4.1
|
4.5
|
7.0
|
||
|
TOTAL MEAN
|
0.0
|
0.0
|
0.0
|
2.8
|
4.1
|
5.1
|
6.7
|
||
|
9.0
|
First
|
I
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
1.4
|
2.3
|
|
II
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
1.7
|
2.7
|
||
|
III
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
1.3
|
2.7
|
||
|
Mean
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
1.4
|
2.5
|
||
|
Second
|
I
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
1.2
|
2.1
|
|
|
II
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
1.6
|
2.5
|
||
|
III
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
1.9
|
2.7
|
||
|
Mean
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
1.5
|
2.4
|
||
|
Third
|
I
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
1.5
|
2.2
|
|
|
II
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
1.9
|
2.5
|
||
|
III
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
2.1
|
2.8
|
||
|
Mean
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
1.8
|
2.5
|
||
|
TOTAL MEAN
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
1.5
|
2.4
|
||
Discussion
The effect of definite
range of pH of Potato Dextrose Agar medium (PDA) was studied on the growth of Fusarium
sp along seven days. The results were observed daily which referred to 4.5 as a
best pH value which led to the maximum growth especially at seventh day. For
the sake of accuracy of the results there are three trails have been made for
each pH value and with each trail triplicates have been done. The optimum
growth of Fusarium sp and most fungi tend to acidic environment more
than alkaline once, so the pH 4.5 was considered a best value and pH 9.0 was
considered worst value for fungal growth. Another study reported that the
optimal pH value for growth of Mucor racemosus is at 4.5 (Le Bars-Bailly
et al. 1999). Similar results were obtained by Panagou et al.
(Panagou et al. 2003); Vali'k et al. (Vali´k, L et al.
1999); Vali'k and Pieckova (Vali’K, L. and E. Pieckova, 2001). However, the
secondary model shows no significant effect of pH on the rate maximum growth of
Mucor racemosus, this has been confirmed both by the results of the
variance analysis. Some mycologists stated that the largest effect of pHs above
pH 4.5 was on fungal growth, and there were opposing pH effects. This resulted
in a 30-fold increase in the relative importance of fungi as indicated by the
growth ratio; the highest ratio was at about pH 4.5 (Bååth, and K. Arnebrant.
1995). The increase in cumulative respiration and biomass accumulation
following substrate addition to soils below pH 4.5 did not differ markedly from
the results for soil samples above pH 4.5, indicating that aluminum toxicity
was not the limiting factor for the microbial communities in this soil.
Irrespective of the mechanism, it is clear that the general inhibitory effects
below pH 4.5 in the acid strip are very different from the pH effects above pH
4.5. For this reason, the analyses of the results and the remainder of the
discussion concerning the influence of pH on microbial parameters focus
exclusively on the pH range above pH 4.5.
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