Bacterial attachment to molybdenite: An electron microscope study
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Bacterial Attachment to Molybdenite: An Electron Microscope Study V. K. BERRY AND L. E. MURR C o n s i d e r a b l e effort has b e e n d i r e c t e d t o w a r d an u n d e r s t a n d i n g of the unique p r o p e r t i e s of m i c r o o r g a n i s m s and t h e i r r e a c t i o n s on m i n e r a l s with h y d r o m e t a l l u r g i c a l p r o c e s s e s . ~-5 The m o s t c o m m o n r e a c t i o n s t h a t have been i n v e s t i g a t e d have b e e n a s s o c i a t e d with the m i c r o o r g a n i s m s i d e n t i f i e d a s
Thiobacillus thiooxidans and Thiobacillus ferroxidans which a r e c h a r a c t e r i s t i c a l l y a u t o t r o p h i c , a e r o b i c b a c t e r i a with the s p e c i f i c a b i l i t y to o x i d i z e s u l f u r both f r o m a s u l f i d e to e l e m e n t a l s u l f u r a s w e l l a s e l e m e n t a l s u l f u r into s u l f u r i c acid. The o x i d a t i o n of h e a v y m e t a l s u l f i d e s into w a t e r s o l u b l e s u l f a t e s and p o l y t h i o n a t e s and f e r r o u s i r o n to f e r r i c i r o n is a c c o m p l i s h e d in a v a r i e t y of e n v i r o n m e n t s , and both b a c t e r i a l g r o u p s have s p e c i e s that function o v e r a wide r a n g e of a c i d i t y and a l k a l i n i t y (or pH), and have high t e m p e r a t u r e t o l e r a n c e s of up to 75~ However, the a b i l i t y of t h e s e m i c r o o r g a n i s m s to grow and function is l i m i t e d e n t i r e l y by the a v a i l a b i l i t y of an e n e r g y s o u r c e and e n v i r o n m e n t a l changes, including t e m p e r ature. A p a r t i c u l a r l y s i g n i f i c a n t f e a t u r e of b a c t e r i a l / m i n e r a l i n t e r a c t i o n involves the m o d e and c h a r a c t e r of b a c t e r i a l a t t a c h m e n t which h a s b e e n v a r i o u s l y d e s c r i b e d a s o c c u r r i n g through a v a r i e t y of h o l d f a s t s , including a d h e s i v e p i l i 6-s a s w e l l a s s u r f a c e a d h e s i o n f l '~8 A f e a t u r e of a t t a c h m e n t which h a s n o t b e e n i n v e s t i g a t e d with r e g a r d to m i n e r a l l e a c h i n g involves the a t t a c h m e n t location. That i s , t h e r e have been no a t t e m p t s to d e t e r m i n e whether o r not the a t t a c h m e n t s i t e is a r e s u l t of r a n d o m s e l e c t i o n , or w h e t h e r a t t a c h m e n t o c c u r s a t r e g i o n s of s p e c i f i c ion c o n c e n t r a tion, s u r f a c e c h e m i s t r y , o r e n e r g e t i c s . With r e g a r d to the l a s t i t e m , it m a y be of i n t e r e s t to d e t e r m i n e whether s u r f a c e d e f e c t s such a s the e m e r g e n c e s i t e s of d i s l o c a t i o n s , c r a c k s , r e g i o n s of s p e c i f i c c r y s t a l l o g r a p h y , s u r f a c e s t e p s o r r e g i o n s of h i g h e r i n t e r n a l o r s p e c i f i c s u r f a c e f r e e e n e r g y r e l a t e d to high d e n s i t i e s of c r y s t a l d e f e c t s influ
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