Hyphal tip growth in Achlya bisexualis. I. Distribution of 1,3-{beta}-glucans in elongating and non-elongating regions of the wall.

We have approached the problem of hyphal tip growth by comparing the cell wall composition of elongating and non-elongating regions of the hyphae of Achlya bisexualis. To ensure that we could distinguish between elongating and non-elongating hyphae, light microscopic observations were used to determine the rates of elongation under growing and non-growing conditions. When elongation was measured in 10 min intervals it was found to consist of fluctuating periods of fast and slow growth rates, in the form of cycles. Even under our growing conditions, however, a very small number of hyphae in a colony are not elongating. SEM analysis revealed that elongating hyphae have tapered apices, whereas non-elongating hyphae have a rounded apex. The major matrix wall components, 1,3-β-glucans, were localized with an indirect immunogold technique specific for these polymers. This method resulted in their localization to all regions of both elongating and non-elongating hyphae, including the apex.