A new simple method for the enumeration of nitrifying bacteria in different environments

Abstract

In this work, a simple, safe and rapid method for enumerating nitrifying bacteria was used as an alternative to traditional harmful chemical methods. The enumeration of nitrifying bacteria was based upon the change of color of the growth media containing pH indicators in response to acid production during nitrification. The oxidation of ammonia to strong acids by nitrifiers leads to pH decrease, which can be detected by pH indicators such as methyl orange (MO), bromocresol green (BCG), methyl red (MR), bromothymol blue (BTB), and phenol red (PhR) using the Most Probable Number (MPN) technique. The use of these pH indicators revealed a higher estimate than the classical chemical methods in all tested samples. Ammonium oxidizer counts always exceeded those of nitrite oxidizers in the surveyed environments. The time required for the detection of growth (positive tubes in MPN) was descending in the following order: MO, BCG, MR, BTB and PhR. The time to detection was shorter for ammonium oxidizers than for nitrite oxidizers. Generally, nitrifier counts were very low in soils compared with farmyard manure or sewage effluent. Incubation periods for both organisms differed from 4 to 8 weeks depended upon the indicator used. Finally, it could be concluded that the use of pH indicators, especially phenol red, as proposed in this study was accurate, sensitive and successfully applicable for the enumeration of nitrifiers in different environments.

Analysis of microbial community and nitrogen transition with enriched nitrifying soil microbes for organic hydroponics

“…17,18,[31][32][33] However, Nitrosomonas and Nitrobacter were difficult to isolate and cultivate, [14][15][16][17][18] thus making it difficult to artificially construct model systems consisting of culturable strains. On the other hand, our Notes: The nitrification process was performed in test tubes with polypeptone NF and soil soak solution as a microbial source at 28°C, 300 rpm.…”

“…14,15) Culture of nitrifying bacteria is difficult because of their sensitivity to many external factors such as pH and temperature change as well as to various organic and inorganic compounds that act as nutrient and energy sources. [14][15][16][17][18] Therefore, intensive studies on the nitrifying microbial community and its interaction with the environment are necessary for establishing efficient methods to control nitrification processes. However, as the complexity of soil makes it difficult to study nitrifying microbial communities properly, a simple sustainable model system is required to enable us to investigate these nitrifying microbial communities.…”

Groundwater Quality Assessment for Drinking Purpose in Gulistan-e-Johar Town, Karachi, Pakistan

“…Strong correlation of NO 3 with K (r 2 = 0.57) and Mg (r 2 = 0.48) clearly indicate that it is mainly sourced from clay minerals where organic matter is available for degradation by bacteria. The oxidation of ammonia to strong acids by nitrifiers leads to pH decrease (Elbanna et al, 2012) which is also evident by the acidic pH in shallow aquifers of Gulistan e Johar.…”

Visible colorimetric growth indicators of Neisseria gonorrhoeae for low-cost diagnostic applications

“…When bacteria are grown in weakly buffered solutions, they release acidic waste products during growth and replication that change the pH of the solution. Thus, a pH indicator that changes color between the starting pH and the final pH of the media can be used to signal that acidic products have been release by viable bacteria [29]. pH indicators have been used in food and environmental monitoring for this purpose [29][30][31].…”

“…Thus, a pH indicator that changes color between the starting pH and the final pH of the media can be used to signal that acidic products have been release by viable bacteria [29]. pH indicators have been used in food and environmental monitoring for this purpose [29][30][31]. For gonorrhea specifically, pH indicators have been shown to detect the presence of penicillinase release by some N. gonorrhoeae strains [32], but the use of pH indicators as a broader viability marker has never been explored.…”