The present study was conducted to isolate and characterise Pb-resistant lactic acid bacteria (LAB), and thus determine their
potential for use as probiotics against Pb toxicity. A total of 107 Pb-resistant LAB strains were isolated from the gut content of
Cyprinus carpio, of which 41 were established to be gram-positive and catalase-negative. Investigation of the Pb-binding ability
of these isolated LAB identified seven strains (P2, P6, P7, P9, P16, P19 and P22) with comparatively high Pb-binding activities.
These were selected for further screening to establish their Pb tolerance, anti-oxidative capacity and in vitro probiotic characteristics.
Strain P16 exhibited both the highest Pb-binding and a relatively good antioxidant capacity. Furthermore, P16 displayed a
high survival rate during 4 h of exposure to both low-pH (2.5–3.5) conditions and 10.0%fish bile, and a strong capacity to adhere
to fish intestinal mucus (62.4%). Furthermore, P16 showed strong antibacterial activities against all tested fish pathogens. Strains
P6, P9, P16, P19 and P22 were susceptible to a range of tested antibiotics, but not to vancomycin. Thus, of the isolated
lactobacilli, strain P16 exhibited the best Pb-binding ability, a high level of antioxidant activity and satisfactory in vitro probiotic
properties. Biochemical and 16S-rRNA gene analyses identified P16 as Lactobacillus reuteri. Thus, the results of the conducted
in vitro tests suggest that the fish-associated P16 Lact. reuteri strain is a promising candidate probiotic, which should undergo
further investigation to assess its suitability for use in protecting against lead-exposure-induced toxicities in aquaculture.

• Characterisation of Lactic Acid Bacteria Isolated from the Gut of Cyprinus carpio That May Be Effective Against Lead Toxicity