The importance of gut flora in health status and metabolism of the host has been well documented in previous studies
]. The development of gut flora is defined by genetics and environmental factors which shape the composition of gut flora in a reproducible manner
]. In a population as diverse as India, with various ethnic groups living in different geographical areas and having different dietary habits, it is expected that these factors would have an effect on the composition of gut microflora. The differences in composition of gut microflora will in turn have an effect on the host. Hence, it is important to focus on exploring the gut microflora in Indian population. There have been very little reports on Indian gut flora, Pandey et al.
focused on micro eukaryotic diversity in infants and Balamuragan et al.
study focused on anaerobic commensals in children and Bifidobacteria in infants
]. We took this opportunity to explore the changes in gut microflora with age within a family. Selecting 3 individuals from the same family means that there is less genetic variation amongst the subjects as compared to non related individuals. A few studies have shown that kinship seems to be involved in determining the composition of the gut microbiota
] and thus selecting related individuals would mean less inter-individual variation in gut flora as compared to unrelated individuals. The subjects are staying in the same house so the variation in the living environmental conditions and feeding habits are lower as compared to individuals staying at different places. Thus, the differences in gut flora observed in this study would be better attributed to changing age. Our results demonstrate that the gut microflora does change within genetically related individuals of different age, living under the same roof. To the best of our knowledge this is the first study focusing on the change in gut flora within a family in Indian population. DGGE analysis (Figure
) showed that different bacterial species dominate the gut flora in different aged individuals within a family; this finding is consistent with the earlier reports
]. The clone library analysis showed that Firmicutes
are the dominant phyla present in human gut flora in our subjects and also confirmed the results of DGGE analysis showing that different bacterial genera are dominating the gut flora in different aged individuals as shown in Figure
. The clone library analysis with Sanger sequencing has limitations of having low depth of sequencing as compared to Next generation sequencing technologies like pyrosequencing, however longer read length obtained by Sanger sequencing are beneficial when mapping the sequence to the species level
]. Fewer than 100 sequences are enough to detect the pattern of variation among the microbial communities in gut of diverse hosts
]. Although clone library analysis would not yield total bacterial diversity, it would give the variation in major bacterial groups within the samples. Recently Zupancic et al.
reported bacterial genera which forms the core gut microbiota of Amish subjects
]. We retrieved the sequences for almost all the genera defined as core microbiota by Zupancic et al.
in our study. This further supports the fact that clone library analysis could be useful in determining the variation in major bacterial phyla in a sample.
A study by Mariat et al.
on European Population showed that the Firmicutes
ratio being 0.4 in Infants which increases to 10.9 in adults and decreases to 0.6 in elderly
]. Somewhat different results were observed by Biagi et al.
in Italian population, the Firmicutes
ratio for adults 3.9 which increased to 5.1 for elderly and decreased to 3.6 for centenarians respectively
]. Moving from young to elderly the Firmicutes
was observed to be decreased in Mariat et al.
study while it increased in Biagi et al.
]. In contrast, in our study we observed a consistent decrease in Firmicutes
number and increase in Bacteroidetes
number with increasing age. This was observed in the clone library analysis and then validated by qPCR. The decrease in Firmicutes
number and increase in Bacteroidetes
suggest that there would be a gradual decrease in Firmicutes
ratio in our subjects with increasing age which further implies that our subjects do not follow the same trend of change in Firmicutes
ratio with age as to what has been reported earlier in European population.
Isolation of strict anaerobes from one of the family showed age related differences in the culturable anaerobic diversity. To the best of our knowledge this is the first study focusing on age related changes in culturable anaerobic diversity from Indian subcontinent. The isolation of Bifidobacterium adolscentis
from infant sample is consistent with the earlier findings that gut flora is dominated by facultative anaerobes in infants as compared to adult gut flora and Bifidobacterium
is one of early anaerobic colonizers of infant gut
]. The isolation of highly diverse novel bacterial species from human gut of Indian individuals with varying age suggests Indian population is a good source to find novel bacterial isolates, and might have a different composition compared to the Western Population studied earlier.
This is a preliminary study which investigates a very unique subset of the human gut microflora where 3 generations of a family are living under the same roof. Although the number of families participating in the study is low, the observations of the study are important in context of human gut flora studies in Indian scenario. Much more in-depth study is required to define the gut flora in Indian population; however this study is the stepping stone towards establishment of the changes in gut microflora with age in Indian population.