Characterization by whole-cell hybridization of bacterial populations associated with shrimp hatchery biofilms

The impact of shrimp larvae development, as well as water and food inputs upon the increase of bacterial populations within the bacterial community of hatchery tank biofilms, was studied. For this study, a total of 68 biofilm samples were collected from concrete tanks at three larvae production times in a commercial shrimp hatchery. Seventeen samples were taken at each larval development stage (Zoea I, Mysis I, postlarvae 1 and postlarvae 16), as well as 37 samples from water, shrimp nauplii and food, introduced into the shrimp hatchery tanks. Culturable and direct bacterial counts were performed and 16S‐rRNA‐targeted oligonucleotide probes were used to quantify the presence of specific bacterial groups. An average of 27–70% of DAPI total cell counts were detected with the EUB338 probe, while the GAM42a probe signal ranged from 1% to 11%. Vibrio‐like bacteria (VLB) counts in TCBS agar ranged from <10 to 10¹ VLB/cm⁻², with a tendency to increase at the last postlarvae stage. The most significant external source of bacteria registered with GAM42a probe and TCBS agar were found in live Artemia nauplii, used as food; nevertheless, biofilms remain with low counts of these groups.