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Morphological analysis and localization of bacterial species that cohabit with Arthrospira sp. using Scanning Electron Microscopy

Abstract:

Arthrospira sp is a filamentous cyanobacterium that has biotechnological importance due to its high protein content and bioactive elements used in the industry.The difficult elimination of bacteria that cohabit with Arthrospira sp. indicates that they could be attached to the surface of the filaments or embedded in the mucilaginous cover of Arthrospira sp., and deterioration of axenic cultures of Arthrospira sp. could imply that these cohabitant bacteria are important for Arthrospira sp. subsistence. In this paper, we use Scanning Electron Microscopy (SEM) to determine the morphology and location of cohabitant bacteria with Arthrospira sp. Lefevre 1963/M-132-1 strain. Cultivable bacteria were obtained from Arthrospira sp. cultures previously washed by filtration (AO sterile culture medium), treated at pH 12 for 72 hours (physic-chemical treatment), and observed (sampled) at two different times: one week after the physic-chemical treatment, and two months after the physic-chemical treatment. The micrographs evidenced that the morphologies of five (5) cultivable isolated bacteria match with the morphology of their molecular identification: Bacillus sp. AP1 (rod-shaped), Halomonas desiderata (rod-shaped), Indibacter alkaliphilus (rod-shaped), Rhodobaca bogoriensis (spherical) and Bacillus akibai (rod-shaped). The SEM of Arthrospira sp. culture gave the following results: in T1 we observed in the culture a pedunculated ovoid bacterial morphology that does not match any of the cultivable bacteria, implying that it is an uncultivable bacterium. The Arthrospira sp. culture observed in T2 effectively showed that the cohabitant bacteria get attached to the surface of the filaments or embedded in the mucilaginous cover of the cyanobacterium.