MicrobiologicalAssessment of the BiofilterMatrixWithin a Biofiltration systemTreating Borehole water in KwaZulu-Natal (SouthAfrica)

Document Type : Original Research Paper


Discipline of Microbiology, School of Life Sciences, University of KwaZulu-Natal, Private Bag X01, Pietermaritzburg 3209, South Africa


To assess the microbiological status of a biofiltration system used to treat borehole water, filter
matrix samples were analyzed after staining for the presence of active biofilms using confocal laser scanning
microscopy (CLSM). CLSM revealed the presence of biofilms on the filter matrix with actively metabolizing
microbial cells present. Thereafter, heterotrophs,manganese oxidizing bacteria (MOB) and iron oxidizing bacteria
(IOB) present in the biofilms were quantified. For heterotrophs a count of 2.9×107 cfu/g was established using
R2A agar while counts for presumptive MOB and IOB were established as 2.4×107 cfu/g and 3.1×107 cfu/g
respectively. In addition, a clone library was established using DNAextracted from a pooled filter matrix sample
to assess the diversity of bacteria present within the biofilter matrix. A total of 100 randomly selected clones
were separated into 14 unique operational taxonomic unit (OTU’s) based upon restriction patterns of amplified
partial 16S rRNA genes. Overall, 38% of the clones were assigned to the phylum Proteobacteria, 13% to the
phylum Actinobacteria, 24% to the phylum Firmicutes, 21% to the phylum Nitrospirae and 4% to the phylum