UPGMA Analysis: An Analysis Of The Microbial Community

RESULT
Microbial community analysis
Table 1 illustrates the phylogenetic affiliation and the similarity of the bands marked in Fig. 4a which shows the bacterial DGGE fingerprint obtained when ferrous sulfate was used as the energy source (batch-1). Initial sludge had 18 dominant bands out of which 7 bands were not detected on the 2nd day (Fig. 4a) due to changes in the physical condition of the sludge such as aeration and the pH decrease. Dynamics in the microbial community profiling was studied using UPGMA analysis and Figure 4b depicts the organization of the clusters when iron oxidizing microorganisms were used in the SDDML process. Lanes 1, 2 and 3 were put in a separate cluster from the rest of the lanes among which lane 2 and lane 3
5a and the phylogenetic affiliation of the marked bands is illustrated in Table 2. UPGMA analysis (Fig. 5b) of the DGGE fingerprint (Fig. 5a), showed that the microbial community was very dynamic in response to the changing conditions such as solids reduction and pH. During the SSDML process, variation in the pH of the sludge resulted in a succession of neutrophiles by mild acidophilic bacteria followed by acidophilic bacteria. This succession is reflected by the cluster analysis. Lane 1 which shows the profile of the initial sludge had 18 dominant bands. Aeration and decrease in pH by 0.69 units were the main reasons for the disappearance of 8 bands on day 2. Lane 1 and lane 2 were put in a separate cluster with less than 40% similarity with the rest of the profiles. As the SSDML process continued, pH decreased due to production of sulfuric acid. In addition to it, system was aerated to maintain the aerobic condition. These were the reason for the resultant clustering of the lane 1 and lane 2 different from the rest of the lanes. Lane 3 and 4 which represent the profile of day 4 and day 6 respectively were grouped together in the same cluster, which showed 40% similarity with cluster including lanes representing 8th, 10th, 12th and 15th day of the operation. Lane 7 (day 12) was 80% similar to lane 8 (day 15) and lane 5 (day 8) was 70% similar to lane 6 day 10). Diversity with respect to
2a) was used but the final pH was low when elemental sulfur (Fig. 2b) was used. Acidithiobacillus ferrooxidans is an autotroph, which uses Fe+2 as an electron donor to obtain energy and in this process Fe+2 is oxidized to Fe+3. Hence, Fe+2 concentration plays an important role in its growth (15). In addition to Acidithiobacillus ferrooxidans, three other heterotrophic microorganisms were detected which can oxidize Fe+2 to Fe+3. Figure 2a shows the variation in concentration of Fe+2 and Fe+3 during the course of SSDML process. Analysis by ion chromatography detected 0.55 g/L of Fe+3 on 0th day because Fe+2 got chemically oxidized to Fe+3 when ferrous sulfate was added into the reactor. Microbial oxidation of Fe+2 to Fe+3 continued till day 10. Afterwards, Fe+3 concentration stabilized from 10th to 15th day of the SSDML process (Fig. 2a). It was observed that the increase in Fe+3 concentration resulted in the corresponding reduction in pH up to the 8th day of the experiment. Average Fe+3 production rate for 15 days of SSDML process was found to be 0.13