CHINESE JOURNAL OF PARASITOLOGY AND PARASITIC DISEASES ›› 2022, Vol. 40 ›› Issue (3): 355-361.doi: 10.12140/j.issn.1000-7423.2022.03.012

• ORIGINAL ARTICLES • Previous Articles     Next Articles

Isolation, identification and the activity of producing digestive enzymes of culturable bacteria from the larval intestine of laboratory line housefly

ZHANG Ke-xin1(), LIU Wen-juan1, ZHANG Xin-yu1, ZHANG Qian1, ZHANG Rui-ling1, ZHANG Zhong1,2,*()   

  1. 1. School of Basic Medical Science, Shandong First Medical University, Tai’an 271016, China
    2. School of Life Science of Shandong First Medical University, Tai’an 271016, China
  • Received:2021-08-24 Revised:2021-10-17 Online:2022-06-30 Published:2022-07-06
  • Contact: ZHANG Zhong E-mail:Zhangkx2020021@126.com;nasonia@163.com
  • Supported by:
    National Natural Science Foundation of China(81572028)

Abstract:

Objective To isolate cultivable bacteria from the intestine of housefly larvae, investigate the activity of digestive enzymes produced by these bacteria, and explore the effects of intestinal bacteria on the digestion of food and the growth and development of housefly larvae. Methods The bacteria in the intestine of housefly larvae were isolated and purified by traditional bacterial isolation and culture method, and 16S rRNA gene sequence was analyzed for molecular identification of identify species. Using the bacteria culture medium of different property to screen the bacteria producing amylase, cellulase, protease, or lipase, and the diameter ratio of hydrolytic circle (D) to bacterial colony (d) was measured to compare the activities of digestive enzymes produced by different bacteria. SPSS 20.0 software was used for statistical analysis. A one-way analysis of variance was used for comparison between groups. Results A total of 9 species of facultative anaerobic bacteria, which belongs to 6 genera, were isolated from the intestines of housefly larvae cultured in an anaerobic environment, among which there were 3 species in Providence (Providencia sneebia DSM 19967, P. rettgeri and P. stuartii), 2 species in Enterococcus (E. casseliflavus and E. faecalis), and 1 specie each in Pseudocitrobacter (P. faecalis), Morganella (M. morganii), Enterobacter (E. hormaechei) and Klebsiella (K. pneumoniae). A total of 10 species of bacteria belonging to 8 genera were isolated from the intestines of housefly larvae cultured in an aerobic environment, among which there were 2 species in Enterobacter (E. hormaechei and E. cloacae), 2 species in Providence (P. stuartii and P. vermicola), and 1 specie each in Klebsiella (K. pneumoniae), Pseudomonas (P. aeruginosa), Acinetobacter (A. bereziniae), Lactococcus (L. lactis), Lysinibacillus (L. fusiformis) and Bacillus (B. safensis). Among these facultative anaerobes were isolated from the intestines of housefly larvae cultured in an anaerobic environment, 9 produced amylase, and 8 produced cellulase and 1 produced lipase; no bacteria produced protease under anaerobic conditions. Among these facultative anaerobes, 9 produced amylase and 8 produced cellulase; no bacteria produced protease and lipase detected in aerobic condition. Under anaerobic conditions, there was no difference in amylase activity among 9 facultative anaerobic culture bacteria (F = 1.953, P > 0.05); among the cellulase activities of 8 facultative anaerobes, E. casseliflavus lead had the strongest cellulase activity, with a D/d value of 1.36 ± 0.06 (F = 3.367, P < 0.05); and only P. rettgeri produced lipase, with a D/d value of 2.28 ± 0.16. In the aerobic state, among the amylase activities of 9 facultative anaerobic bacteria, E. faecalis had the strongest amylase-producing activity, and the D/d value of 1.42 ± 0.06 (F = 3.881, P < 0.05). Among the cellulase activities of 8 facultative anaerobes, E. casseliflavus had the strongest cellulase activity, with a D/d value of 1.29 ± 0.01(F = 6.633, P < 0.05). Among aerobic bacteria, P. aeruginosa and B. safensis produced protease, with D/d values of 3.67 ± 0.25 and 3.58 ± 0.31 (F = 0.087, P > 0.05); and only K. pneumoniae produced amylase, with a D/d value of 4.83 ± 0.12; no bacteria produced cellulase and lipase. Conclusion The composition of cultivable bacteria in the intestine of housefly larvae is relatively unitary, but most anaerobic bacteria and aerobic bacteria have the function of secreting digestive enzymes.

Key words: Housefly larvae, Intestinal anaerobic bacteria, Intestinal aerobic bacteria, Digestive enzyme-producing bacteria

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