Scanning Electron Microscopic Observation of Bacteria Attached to Titanium and Aluminum Alloy Plates

Abstract

Plates of titanium and aluminum alloy were immersed in seawater at Okunouchi Bay of Kurahashi island, Seto Inland Sea to investigate the initial process of marine microbiofouling during the period from April to June, 1983. After 10, 25, 36 and 51 dayimmersion, the solid surfaces were observed by scanning electron microscope and the fouling bacteria were isolated and characterized. The results obtained are summarized as follows:(1) The mean density of the bacteria attached to the solid surfaces increased with the lapse of the immersion period. That is, after 10 day-immersion they were 2.5×103cells/mm2 and 1.2×104cells/mm2 on the titanium and aluminum alloy plate, respectively. And after 51 day-immersion they amounted to 3×105cells/mm2 on both materials.(2) The kinds of bacteria attached to the solid surfaces changed with the length of the immersion period, that is, the first colonizer on titanium plate was small rods, and then stalked bacteria, cocci and short rods appeared in turn. In the case of aluminum alloy plate, the first colonizers were small rods, and then budding, stalked and filamentous bacteria and short rods proliferated. As a result, it is reasonable to say that the bacterial communities on the immersed plate surfaces depend on the kinds of materials used for the fouling experiments.(3) Bacteria attached to two kinds of plates immersed for 36 days were cultivated on the nutrient-enriched agar medium, isolated and characterized. Two of three strains isolated from titanium plate were determined to be Pseudomonas and Flavobacterium, and two strains isolated from aluminum alloy plate were determined to be Vibrio and Achromobacter.