Discussion:-
This
body of work has largely been concerned with bacteriocin production from the
E.coli. The bacteriocins are the proteinaceous substance act as the
bactericidal agent that inhibit and often kill the some closely related species
of the bacteria. Bacteriocins inhibit
the spoilage of food and also pathogenic bacteria.Bacteriocins are produced by
both type of bacteria Gram –ve and Gram +ve bacteria. The bacteriocins from
E.coli are of two type’scolicin which occupies the large molecular weight and
microcin with low molecular weight. In this we only check that either
bacteriocin produced from our isolated strains of E.coli or not.
We
began this study by collecting the samples. The E.coli is belonging to the
Enterobacteriaceae family it commonly found in gut flora of humans and animals.
In the first step design the criteria how to collect sample we isolate pure
cultures of E.coli by streaking method. Than by ager overlay method check the
bacteriocin production but in the later studies the bacteriocin production was
measured in the quantitative way but here our data is represent only which
strain produced bacteriocin and which not. In our conducted study result
indicates that 70% of E.coli strains
produced bacteriocins.
In
the next step we check the bacteriocin effect with different strains of
S.aureus. Our results only explain the inhibitory effect on the S.aureus and
have no quantitative data and shows that the S.aureus strains were inhibited by
bacteriocins of E.coli but at very low level.The extracts from E.coli showed
zones of inhibition against different pathogenic strains of diverse bacteria
Staphylococcus aureus.
As
in a study by Yang, et. al., a very
little amount of bacteriocins was isolated due to adsorption on to the cell
surface
The
varied range of inhibition zones was observed but we cannot measure it.
Sometime the bacteria acquired resistance against bacteriocins. such as in the
study of Michael Feld garden and Margaret A. Riley in 1997 present survey of colicin resistance in 158 E. coli
isolates from a variety of hosts. They have screened for resistance in 137
isolates of non-E.coli enteric, which are close relatives of E. coli. Their
data suggest that resistance levels are high. Similarly high levels of
interspecific resistance to colicins are also observed. The frequency of
colicin resistance to eighteen colicins is exceptionally high in all four E.
coli collections surveyed. On average, 75% of the strains surveyed were
resistant to a particular colicin.
Similarly
Riley and Gordon in 1996 do the surveys of over 1000 isolates reveal that, on
average, 30% of E. coli produce colicin.
In
earlier study the David and Claire in 2005collect the 266 faecal isolates of
Escherichia coli from humans was assayed for the production bacteriocins and
screened using a PCR-based method for the presence of eleven colicins and seven
microcins.
Our
results are also in compliance of the previous work performed by Savadagoet
al.(2006). However, in contrast, they have isolated eight strains of lactic
acid bacteria from fermentedmilk to produce bacteriocins. Isolated bacteriocin
showed inhibitory activity against Enterococcus faecalis, Bacillus cereus, Staphylococcus
aureus and Escherichia coli. Gram-positive indicator bacteria were most
inhibited. Their results indicate that the isolated strains of lactic acid bacteria
are able to synthesize inhibitory substances against pathogenic bacteria. These
inhibitory substances act differently on pathogenic reference indicator
bacteria.
A
recent study conducted by Adesokan et al. (2008) have observed less inhibitory
activity against Gram negative bacteria as compared to Gram positive bacteria
by studying the effect of bacteriocin on Staphylococcus aureus, Pseudomonas aeroginosa and Escherichia coli. It has been observed that
the inhibiting substances produced by lactic acid bacteria are generally
protein in nature (Klaenhammer, 1993).
In
contrast to our work Goraya, et.al in
2013 determine the Antibacterial activity of bacteriocins from LAB was
evaluated against known food spoiling bacteria such as Escherichia coli,
Enterococcus faecalis and Staphylococcus
aureus (obtained from Institute of Microbiology
UAF Faisalabad).A disc diffusion assay procedure was followed for it and
measure the zone of inhibition.Most inhibited strain were Staphylococcus aureus
and Enterococcus faecalis
.
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