Diversity of beta-propeller phytase genes in the intestinal contents of grass carp provides insight into the release of major phosphorus from phytate in nature.
Phytate is the most abundant organic phosphorus compound in nature, and microbial mineralization of phytate by phytase is a key process for phosphorus recycling in the biosphere. In the present study, beta-propeller phytase (BPP) gene fragments were readily amplified from the intestinal contents of grass carp (Ctenopharyngodon idellus) directly or from phytate-degrading isolates from the same source, confirming the widespread occurrence of BPP in aquatic communities. The amounts of sequences collected using these two methods differed (88 distinct genes versus 10 isolates), but the sequences showed the same general topology based on phylogenetic analysis. All of the sequences fell in five clusters and were distinct from those of Anabaena, Gloeobacter, Streptomyces, Flavobacterium, Prosthecochloris, and Desulfuromonas, which have never been found in the grass carp intestine. Analysis of the microbial diversity by denaturing gradient gel electrophoresis demonstrated that unculturable bacteria were dominant bacteria in the grass carp intestine and thus the predominant phytate-degrading organisms. The predominant cultured species corresponding to the phytate-degrading isolates, Pseudomonas, Bacillus and Shewanella species, might be the main source of known BPPs. A phytase from Brevundimonas was first obtained from cultured species. Combining our results with Lim et al.'s inference that phytate-mineralizing bacteria are widely distributed and highly diverse in nature (B. L. Lim, P. Yeung, C. Cheng, and J. E. Hill, ISME J. 1:321-330, 2007), we concluded that BPP is the major phytate-degrading enzyme in nature, that most of this enzyme might originate from unculturable bacteria, and that the distribution of BPP may be related to the type of niche. To our knowledge, this is the first study to experimentally estimate BPP diversity in situ.
Huang
Huoqing
H
Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, No. 12 Zhongguangcun Street, Beijing 100081, People's Republic of China.
Shi
Pengjun
P
Wang
Yaru
Y
Luo
Huiying
H
Shao
Na
N
Wang
Guozeng
G
Yang
Peilong
P
Yao
Bin
B
D010832:6-Phytase / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D001419:Bacteria / Q000145:classification* / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D002347:Carps / Q000382:microbiology*; D016000:Cluster Analysis; D005766:Gastrointestinal Contents / Q000382:microbiology*; D008969:Molecular Sequence Data; D010758:Phosphorus / Q000378:metabolism*; D010802:Phylogeny; D010833:Phytic Acid / Q000378:metabolism*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017385:Sequence Homology
D010758:Phosphorus; D010833:Phytic Acid; D010832:6-Phytase