من انا

صورتي
الرياض, Saudi Arabia
مسلم، وأناأحوج ما أكون إلى معرفة نفسي

الثلاثاء، 31 يناير، 2012

Effect of pH values on the growth of Fusarium species


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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