摘要
目的
表皮葡萄球菌(Staphylococcus epidermidis)是一种凝固酶阴性、革兰氏染色阳性的球菌,广泛存在于皮肤、母乳和血液等环境中。母乳中的细菌对婴幼儿肠道初始菌群的建立及免疫力的提高具有至关重要的作用,本研究通过比较基因组学分析,以期了解母乳源表皮葡萄球菌的遗传多样性和功能基因特征。
方法
使用Illumina NovaSeq高通量测序平台,对前期分离自健康母乳中的110株表皮葡萄球菌进行基因组测序,并结合NCBI已公开的263株皮肤源、血液源和母乳源表皮葡萄球菌的基因组序列进行比较基因组学分析。
结果
373株表皮葡萄球菌的基因组大小为(2.50±0.33) Mb,G+C含量为(32.0±0.1)%,编码序列(coding sequence, CDs)数量为(2 331±368)个。不同分离源的菌株在基因组大小和CDs数量上均存在显著差异(P<0.05),其中血液源菌株的基因组较大且CDs数量较多。系统发育树结果显示,表皮葡萄球菌在系统发育树上呈现一定的分离源聚类趋势,体内分离源(母乳源和血液源)菌株的亲缘关系更近。不同分离源的菌株在携带毒力因子和耐药基因的数量上也存在显著差异(P<0.05),血液源菌株携带的毒力基因和耐药基因种类最多,而母乳源菌株携带毒力基因和耐药基因种类最少。
结论
表皮葡萄球菌为了适应不同生境发生了适应性进化。相较于皮肤源和血液源菌株,母乳源菌株在生物膜合成相关基因、耐药基因及毒力因子的携带率上较低。本研究为表皮葡萄球菌的适应性进化提供了新的见解,并为后续母乳源分离株遗传背景的相关研究提供了一定的理论依据。
表皮葡萄球菌(Staphylococcus epidermidis)广泛存在于皮肤、环境及母乳
母乳最初被认为是无菌的液体。然而,随着对母乳研究的不断深入,现在普遍认为母乳中存在着丰富的微生物资源。2007年,Martín
目前关于母乳源表皮葡萄球菌的研究主要集中在检出和鉴定层面,缺乏对其遗传特性的深入研究。因此,本研究采用Illumina NovaSeq高通量测序平台,对前期从母乳中分离得到的110株表皮葡萄球菌进行基因组测序,并结合NCBI RefSeq数据库 (https://www.ncbi.nlm.nih.gov)下载的120株皮肤分离源表皮葡萄球菌、101株血液分离源表皮葡萄球菌及42株母乳源表皮葡萄球菌菌株基因组进行比较基因组学分析,以期解析母乳源表皮葡萄球菌的功能特征及进化历程。
1 材料与方法
1.1 实验菌株
本研究依托内蒙古农业大学乳酸菌种质资源库,对前期分离自母乳中的110株表皮葡萄球菌进行基因组测序(经内蒙古农业大学科学研究和学术伦理专业委员会批准,批准号为2018-059),并结合NCBI RefSeq数据库中血液源分离株(101株)、皮肤源分离株(120株)及母乳源分离株(42株)的全基因组序列进行分析。110株母乳源表皮葡萄球菌基因组序列已上传至国家微生物科学数据中心(https://nmdc.cn/resource/genomics/genome/detail/NMDC60198554),菌株相关信息见
菌株号 Strain number | GCF/NMDC号 GCF/NMDC number | 分离源 Source | 菌株号 Strain number | GCF/NMDC号 GCF/NMDC number | 分离源 Source |
---|---|---|---|---|---|
HTM3 | NMDC20304984 | Milk | BJM64-3 | NMDC20305025 | Milk |
HTM4 | NMDC20304985 | Milk | BJM64-4 | NMDC20305026 | Milk |
BJM60-10 | NMDC20304986 | Milk | BJM64-8 | NMDC20305027 | Milk |
BJM60-11 | NMDC20304987 | Milk | BJM64-9 | NMDC20305028 | Milk |
BJM60-12 | NMDC20304988 | Milk | BJM65-10 | NMDC20305029 | Milk |
BJM60-1 | NMDC20304989 | Milk | BJM65-11 | NMDC20305030 | Milk |
BJM60-2 | NMDC20304990 | Milk | BJM65-12 | NMDC20305031 | Milk |
BJM60-3 | NMDC20304991 | Milk | BJM65-1 | NMDC20305032 | Milk |
BJM60-4 | NMDC20304992 | Milk | BJM65-2 | NMDC20305033 | Milk |
BJM60-5 | NMDC20304993 | Milk | BJM65-3 | NMDC20305034 | Milk |
BJM60-6 | NMDC20304994 | Milk | BJM65-4 | NMDC20305035 | Milk |
BJM60-7 | NMDC20304995 | Milk | BJM65-5 | NMDC20305036 | Milk |
BJM60-8 | NMDC20304996 | Milk | BJM65-7 | NMDC20305037 | Milk |
BJM60-9 | NMDC20304997 | Milk | BJM65-9 | NMDC20305038 | Milk |
BJM61-11 | NMDC20304998 | Milk | BJM66-4 | NMDC20305039 | Milk |
BJM61-1 | NMDC20305000 | Milk | BJM67-1 | NMDC20305040 | Milk |
BJM61-2 | NMDC20304999 | Milk | BJM67-2 | NMDC20305041 | Milk |
BJM61-3 | NMDC20305001 | Milk | BJM67-4 | NMDC20305042 | Milk |
BJM61-4 | NMDC20304984 | Milk | BJM67-5 | NMDC20305043 | Milk |
BJM61-5 | NMDC20304985 | Milk | BJM67-6 | NMDC20305044 | Milk |
BJM61-6 | NMDC20304986 | Milk | Cai-13 | NMDC20305045 | Milk |
BJM61-7 | NMDC20304987 | Milk | CLJ-2 | NMDC20305046 | Milk |
BJM61-8 | NMDC203049B8 | Milk | CLJ-3 | NMDC20305047 | Milk |
BJM61-9 | NMDC20304989 | Milk | EFR17-12 | NMDC20305048 | Milk |
BJM62-10 | NMDC20304990 | Milk | EFR17-15 | NMDC20305049 | Milk |
BJM62-11 | NMDC20304991 | Milk | EFR17-18 | NMDC20305050 | Milk |
BJM62-12 | NMDC20304992 | Milk | EFR17-21 | NMDC20305051 | Milk |
BJM62-1 | NMDC20304993 | Milk | EFR17-3 | NMDC20305052 | Milk |
BJM62-2 | NMDC20304994 | Milk | EFR9-11 | NMDC20305053 | Milk |
BJM62-3 | NMDC20304995 | Milk | EFR9-12 | NMDC20305054 | Milk |
BJM62-4 | NMDC20304996 | Milk | EFR9-13 | NMDC20305055 | Milk |
BJM62-6 | NMDC20304997 | Milk | EFR9-4 | NMDC20305056 | Milk |
BJM62-7 | NMDC20304998 | Milk | EFR9-7 | NMDC20305057 | Milk |
BJM62-8 | NMDC20305000 | Milk | EFR9-8 | NMDC20305058 | Milk |
BJM62-9 | NMDC20304999 | Milk | EFR9-9 | NMDC20305059 | Milk |
BJM63-13 | NMDC20305001 | Milk | EYR1-14 | NMDC20305060 | Milk |
BJM63-14 | NMDC20304984 | Milk | EYR1-16 | NMDC20305061 | Milk |
BJM63-1 | NMDC20304985 | Milk | EYR1-2 | NMDC20305062 | Milk |
BJM63-2 | NMDC20304986 | Milk | EYR2-10-1 | NMDC20305063 | Milk |
BJM63-3 | NMDC20304987 | Milk | EYR2-10-2 | NMDC20305064 | Milk |
BJM64-12 | NMDC20305002 | Milk | EYR2-12 | NMDC20305065 | Milk |
EYR2-13-1 | NMDC20305066 | Milk | APC3789 | GCF_009897435.1 | Milk |
EYR2-4-2 | NMDC20305067 | Milk | APC3882 | GCF_009897505.1 | Milk |
EYR4-2 | NMDC20305068 | Milk | APC3780 | GCF_009897515.1 | Milk |
EYR5-15 | NMDC20305069 | Milk | APC3779 | GCF_009897605.1 | Milk |
EYR5-19-2 | NMDC20305070 | Milk | APC3778 | GCF_009897625.1 | Milk |
EYR7-1 | NMDC20305071 | Milk | APC3776 | GCF_009897655.1 | Milk |
EYR7-6 | NMDC20305072 | Milk | APC3777 | GCF_009897685.1 | Milk |
GRM-6-2 | NMDC20305073 | Milk | APC3775 | GCF_009897805.1 | Milk |
HLR12-3-1 | NMDC20305074 | Milk | APC3810 | GCF_009897825.1 | Milk |
HLR2-2 | NMDC20305075 | Milk | APC3764 | GCF_009897905.1 | Milk |
HLR4-1 | NMDC20305076 | Milk | APC3761 | GCF_009897925.1 | Milk |
NXF-3 | NMDC20305077 | Milk | APC3762 | GCF_009897935.1 | Milk |
WLN-1 | NMDC20305078 | Milk | APC3772 | GCF_009897945.1 | Milk |
WLN-2 | NMDC20305079 | Milk | APC3763 | GCF_009897975.1 | Milk |
WLN-4 | NMDC203050B0 | Milk | APC3768 | GCF_009898025.1 | Milk |
WLN-5 | NMDC203050B1 | Milk | APC3769 | GCF_009898035.1 | Milk |
WM-2 | NMDC20305082 | Milk | APC3771 | GCF_009898055.1 | Milk |
WY-6 | NMDC20305083 | Milk | APC3785 | GCF_009898115.1 | Milk |
YJQ-1 | NMDC20305084 | Milk | APC3808 | GCF_009896645.1 | Milk |
YLL-3 | NMDC20305085 | Milk | APC3784 | GCF_009896875.1 | Milk |
YLR-2 | NMDC20305086 | Milk | APC3783 | GCF_009896905.1 | Milk |
YLR-4 | NMDC20305087 | Milk | APC3807 | GCF_009896915.1 | Milk |
YLR-5 | NMDC20305088 | Milk | APC3782 | GCF_009896965.1 | Milk |
YLR-6 | NMDC20305089 | Milk | APC3806 | GCF_009896975.1 | Milk |
YLR-7 | NMDC20305090 | Milk | APC3804 | GCF_009897025.1 | Milk |
YLR-8 | NMDC20305091 | Milk | APC3803 | GCF_009897035.1 | Milk |
ZJH-1 | NMDC20305092 | Milk | APC3802 | GCF_009897065.1 | Milk |
ZJH-3 | NMDC20305093 | Milk | APC3800 | GCF_009897075.1 | Milk |
APC3801 | GCF_009897085.1 | Milk | A11 | GCF_004329455.1 | Skin |
APC3799 | GCF_009897125.1 | Milk | ADQBG | GCF_036419715.1 | Skin |
APC3883 | GCF_009897145.1 | Milk | ADQBK | GCF_036419775.1 | Skin |
APC3797 | GCF_009897165.1 | Milk | AH6072 | GCF_025665415.1 | Skin |
APC3798 | GCF_009897195.1 | Milk | CDC120 | GCF_003856395.1 | Skin |
APC3795 | GCF_009897225.1 | Milk | CDC121 | GCF_003856455.1 | Skin |
APC3781 | GCF_009897235.1 | Milk | HD33 | GCF_006337225.1 | Skin |
APC3794 | GCF_009897265.1 | Milk | HD43 | GCF_006337205.1 | Skin |
APC3793 | GCF_009897305.1 | Milk | HD66 | GCF_006337185.1 | Skin |
APC3792 | GCF_009897315.1 | Milk | JH | GCF_012029995.1 | Skin |
APC3791 | GCF_009897335.1 | Milk | JH-S-1 | GCF_016107425.1 | Skin |
APC3790 | GCF_009897365.1 | Milk | JH-S-3 | GCF_016107415.1 | Skin |
APC3788 | GCF_009897375.1 | Milk | JONWP017 | GCF_037699445.1 | Skin |
APC3787 | GCF_009897425.1 | Milk | JONWP018 | GCF_037699365.1 | Skin |
JONWP026 | GCF_037699085.1 | Skin | JONWP070 | GCF_037697275.1 | Skin |
JONWP027 | GCF_037699045.1 | Skin | JONWP071 | GCF_037697195.1 | Skin |
JONWP028 | GCF_037698945.1 | Skin | JONWP072 | GCF_037697235.1 | Skin |
JONWP029 | GCF_037698925.1 | Skin | JONWP073 | GCF_037697155.1 | Skin |
JONWP030 | GCF_037698845.1 | Skin | JONWP074 | GCF_037697115.1 | Skin |
JONWP031 | GCF_037698905.1 | Skin | JONWP075 | GCF_037697035.1 | Skin |
JONWP032 | GCF_037698885.1 | Skin | JONWP076 | GCF_037697055.1 | Skin |
JONWP033 | GCF_037698725.1 | Skin | JONWP077 | GCF_037696995.1 | Skin |
JONWP035 | GCF_037698685.1 | Skin | JONWP079 | GCF_037696835.1 | Skin |
JONWP036 | GCF_037698705.1 | Skin | JONWP080 | GCF_037696875.1 | Skin |
JONWP037 | GCF_037698745.1 | Skin | JONWP081 | GCF_037696855.1 | Skin |
JONWP038 | GCF_037698585.1 | Skin | JONWP082 | GCF_037696795.1 | Skin |
JONWP039 | GCF_037698525.1 | Skin | JONWP083 | GCF_037696755.1 | Skin |
JONWP040 | GCF_037698485.1 | Skin | JONWP084 | GCF_037696655.1 | Skin |
JONWP041 | GCF_037698495.1 | Skin | JONWP085 | GCF_037696675.1 | Skin |
JONWP042 | GCF_037698465.1 | Skin | JONWP086 | GCF_037696635.1 | Skin |
JONWP043 | GCF_037698405.1 | Skin | JONWP087 | GCF_037696595.1 | Skin |
JONWP044 | GCF_037698325.1 | Skin | JONWP088 | GCF_037696575.1 | Skin |
JONWP045 | GCF_037698295.1 | Skin | JONWP089 | GCF_037696455.1 | Skin |
JONWP046 | GCF_037698245.1 | Skin | JONWP090 | GCF_037696475.1 | Skin |
JONWP047 | GCF_037698285.1 | Skin | JONWP091 | GCF_037696435.1 | Skin |
JONWP048 | GCF_037698225.1 | Skin | JONWP092 | GCF_037696395.1 | Skin |
JONWP049 | GCF_037698145.1 | Skin | JONWP093 | GCF_037696335.1 | Skin |
JONWP050 | GCF_037698115.1 | Skin | JONWP094 | GCF_037696235.1 | Skin |
JONWP051 | GCF_037698045.1 | Skin | JONWP096 | GCF_037696275.1 | Skin |
JONWP052 | GCF_037698065.1 | Skin | JONWP099 | GCF_037696055.1 | Skin |
JONWP053 | GCF_037698105.1 | Skin | JONWP100 | GCF_037696075.1 | Skin |
JONWP054 | GCF_037697945.1 | Skin | JONWP101 | GCF_037696015.1 | Skin |
JONWP055 | GCF_037697845.1 | Skin | JONWP102 | GCF_037696035.1 | Skin |
JONWP056 | GCF_037697895.1 | Skin | JONWP103 | GCF_037695885.1 | Skin |
JONWP057 | GCF_037697865.1 | Skin | JONWP104 | GCF_037695865.1 | Skin |
JONWP059 | GCF_037697725.1 | Skin | JONWP105 | GCF_037695845.1 | Skin |
JONWP060 | GCF_037697685.1 | Skin | JONWP106 | GCF_037695775.1 | Skin |
JONWP061 | GCF_037697695.1 | Skin | JONWP107 | GCF_037695695.1 | Skin |
JONWP062 | GCF_037697625.1 | Skin | JONWP108 | GCF_037695655.1 | Skin |
JONWP063 | GCF_037697525.1 | Skin | JONWP109 | GCF_037695615.1 | Skin |
JONWP064 | GCF_037697565.1 | Skin | JONWP124 | GCF_037700335.1 | Skin |
JONWP065 | GCF_037697475.1 | Skin | JONWP152 | GCF_037694235.1 | Skin |
JONWP066 | GCF_037697495.1 | Skin | JONWP164 | GCF_037693745.1 | Skin |
JONWP067 | GCF_037697415.1 | Skin | VSE1 | GCF_003979615.1 | Skin |
JONWP068 | GCF_037697315.1 | Skin | VSE2 | GCF_003979655.1 | Skin |
JONWP097 | GCF_037696195.1 | Skin | SE54 | GCF_008922375.1 | Blood |
BB403117S | GCF_008922545.1 | Blood | SE56 | GCF_008922385.1 | Blood |
BB403149G | GCF_008922525.1 | Blood | SE58 | GCF_008922365.1 | Blood |
BB403169X | GCF_008923145.1 | Blood | SE59 | GCF_008922345.1 | Blood |
BB405012Y | GCF_008922485.1 | Blood | SE60 | GCF_008922265.1 | Blood |
BB405684Z | GCF_008922505.1 | Blood | SE63 | GCF_008922315.1 | Blood |
BB409909V | GCF_008923085.1 | Blood | SE64 | GCF_008922285.1 | Blood |
BB411089T | GCF_008923045.1 | Blood | SE66 | GCF_008922245.1 | Blood |
BB411582T | GCF_008923005.1 | Blood | SE67 | GCF_009026095.1 | Blood |
BB412943 | GCF_008922995.1 | Blood | SE68 | GCF_009026065.1 | Blood |
BB413468Z | GCF_008922985.1 | Blood | SE69 | GCF_009026045.1 | Blood |
BB413483J | GCF_008922955.1 | Blood | SE70 | GCF_008922205.1 | Blood |
BB417762 | GCF_008922945.1 | Blood | SE73 | GCF_008922175.1 | Blood |
BB418619Q | GCF_008922925.1 | Blood | SE74 | GCF_008922155.1 | Blood |
BB420483A | GCF_008922885.1 | Blood | SE75 | GCF_008922165.1 | Blood |
BB421362A | GCF_008922895.1 | Blood | SE78 | GCF_008922115.1 | Blood |
BB424986M | GCF_008922855.1 | Blood | SE79 | GCF_008922095.1 | Blood |
BB424987J | GCF_008922845.1 | Blood | SE83 | GCF_008922045.1 | Blood |
BB431156H | GCF_008922805.1 | Blood | VCU014 | GCF_000626815.1 | Blood |
BB431437E | GCF_008922785.1 | Blood | LRKNS092 | GCF_001658805.1 | Blood |
BB434495N | GCF_008922795.1 | Blood | LRKNS093 | GCF_001658815.1 | Blood |
BB436056Y | GCF_008922745.1 | Blood | LRKNS111 | GCF_001662985.1 | Blood |
BB436246W | GCF_008922755.1 | Blood | LRKNS112 | GCF_001663025.1 | Blood |
BB437325D | GCF_008922725.1 | Blood | LRKNS113 | GCF_001663015.1 | Blood |
BB437754V | GCF_008922695.1 | Blood | LRKNS114 | GCF_001662145.1 | Blood |
BB438257K | GCF_008922655.1 | Blood | LRKNS115 | GCF_001662175.1 | Blood |
BB440693L | GCF_008922645.1 | Blood | LRKNS116 | GCF_001662165.1 | Blood |
BB441771A | GCF_008922605.1 | Blood | LRKNS117 | GCF_001662155.1 | Blood |
BB442838N | GCF_008922565.1 | Blood | LRKNS118 | GCF_001662225.1 | Blood |
BB443408J | GCF_008922555.1 | Blood | Lt3p20 | GCF_001658905.1 | Blood |
M0026 | GCF_000551165.1 | Blood | M15_2005 | GCF_026157025.1 | Blood |
M0881 | GCF_000362145.1 | Blood | NGS-ED-1107 | GCF_000966705.1 | Blood |
NIH04003 | GCF_000276005.1 | Blood | NGS-ED-1109 | GCF_000966715.1 | Blood |
NIH04008 | GCF_000276085.1 | Blood | NGS-ED-1110 | GCF_000966815.1 | Blood |
NIH05001 | GCF_000276105.1 | Blood | NGS-ED-1111 | GCF_000966755.1 | Blood |
NIH05003 | GCF_000276025.1 | Blood | NGS-ED-1117 | GCF_000966765.1 | Blood |
NIH05005 | GCF_000276125.1 | Blood | NGS-ED-1118 | GCF_000966775.1 | Blood |
NIH06004 | GCF_000276045.1 | Blood | SH03_17 | GCF_002799485.1 | Blood |
NIH08001 | GCF_000276065.1 | Blood | SH05_16 | GCF_002799505.1 | Blood |
SE48 | GCF_008922455.1 | Blood | SH06_17 | GCF_002799565.1 | Blood |
SE49 | GCF_008922445.1 | Blood | TMDU-128 | GCF_024204725.1 | Blood |
SE53 | GCF_008922415.1 | Blood | VSE37 | GCF_003956755.1 | Skin |
TMDU-137 | GCF_024204745.1 | Blood | VSE39 | GCF_003956885.1 | Skin |
TMDU-190 | GCF_024204765.1 | Blood | VSE4 | GCF_003979705.1 | Skin |
VSE36 | GCF_003980285.1 | Skin | VSE41 | GCF_003956805.1 | Skin |
TMDU-265 | GCF_024204785.1 | Blood | VSE42 | GCF_003956875.1 | Skin |
TMDU-300 | GCF_024204805.1 | Blood | VSE43 | GCF_003956905.1 | Skin |
TMDU-302 | GCF_024204825.1 | Blood | VSE44 | GCF_003980205.1 | Skin |
TMDU-323 | GCF_024204845.1 | Blood | VSE46 | GCF_003956995.1 | Skin |
TMDU-41 | GCF_024204705.1 | Blood | VSE47 | GCF_003956955.1 | Skin |
TSM-18 | GCF_024204905.1 | Blood | VSE49 | GCF_003956785.1 | Skin |
TSM-31 | GCF_024204885.1 | Blood | VSE5 | GCF_003979695.1 | Skin |
TSM-36 | GCF_024204925.1 | Blood | VSE50 | GCF_003980275.1 | Skin |
TSM-47 | GCF_024204945.1 | Blood | VSE52 | GCF_003956965.1 | Skin |
TSM-50 | GCF_024204965.1 | Blood | VSE53 | GCF_003956975.1 | Skin |
TSM-51 | GCF_024204985.1 | Blood | VSE54 | GCF_003956855.1 | Skin |
HESN016B | GCF_015070675.1 | Blood | VSE56 | GCF_003980255.1 | Skin |
HESN103B | GCF_015070395.1 | Blood | VSE57 | GCF_003956865.1 | Skin |
IRL01 | GCF_009685135.1 | Blood | VSE58 | GCF_003957035.1 | Skin |
C03 | GCF_015645175.1 | Blood | TMDU-2014-62 | GCF_024204865.1 | Blood |
VSE3 | GCF_003979715.1 | Skin | JONWP025 | GCF_037699105.1 | Skin |
VSE35 | GCF_003956765.1 | Skin | JONWP069 | GCF_037697355.1 | Skin |
Mt1p16 | GCF_001683645.1 | Blood |
1.2 主要试剂和仪器
LB培养基,OXOID公司;琼脂,厦门市赫凯生物科技有限公司;Tiangen试剂盒,天根生化科技(北京)有限公司。
电热恒温水浴锅,生化培养箱,上海一恒科学仪器有限公司;超微量紫外分光光度计,NanoDrop公司;电子天平,奥豪斯仪器(上海)有限公司;全自动高压干热灭菌器,SANYO公司;高压蒸汽灭菌锅,TOMY公司;漩涡振荡器,Scientific Industries公司;超净工作台,上海智城分析仪器制造有限公司;光学显微镜,奥林巴斯(中国)公司;超纯水系统,昆山总馨机械有限公司。
1.3 菌株活化、基因组DNA的提取及基因组测序
挑取单个菌落于LB液体培养基中,置于37 ℃有氧条件下4 000 r/min培养24 h后传代培养至二代,将二代菌液以2%的接种量接种于35 mL液体培养基中,置于37 ℃有氧条件下扩大培养。培养24 h后,菌液以3 000×g离心5 min,弃上清,使用PBS缓冲溶液洗涤菌液2次,再加入5 mL缓冲液,抽取1 mL菌液以3 000×g离心5 min后,收集细菌菌体。使用十六烷基三甲基溴化铵法(cetyltrimethylammonium bromide, CTAB法)提取表皮葡萄球菌的基因组DN
构建约400 bp的文库,并使用Illumina NovaSeq 6000高通量测序平台进行测序,选取150 bp构建pair-end (PE)测序文库,高质量数据平均覆盖度在500×左右。菌株基因组测序委托北京诺禾致源生物科技股份有限公司完成。
使用Trimmomatic软
1.4 基因组组装
使用readfq.v5软件对数据进行进一步过滤,保留500×左右的高质量数据。使用SOAPdenove2软
1.5 比较基因组分析
1.5.1 平均核苷酸一致性(average nucleotide identity, ANI)计算
参考Jain
1.5.2 菌群泛-核心基因集构建
利用Prokka软
1.5.3 系统发育树构建
利用Prokka软
1.5.4 功能基因组预测和注释
将Prokka软
1.5.5 耐药基因注释
通过耐药基因数据库(comprehensive antibiotic resistance database, CARD)(http://arpcard.memaster.ca)对373株表皮葡萄球菌进行耐药基因分析。将表皮葡萄球菌蛋白序列与耐药基因数据
1.5.6 毒力基因注释
通过毒力基因数据库(virulence factors of pathogenic bacteria, VFDB) (http://www.mgc.ac.cn/VFs/main.htm
1.5.7 统计学分析及数据可视化
使用R软件(v4.2.2)对数据进行统计学分析和数据可视化。利用iTol网
2 结果与分析
2.1 表皮葡萄球菌基因组基本信息
对373株表皮葡萄球菌基因组质量评估发现,所有菌株的完整性均>95%,污染度<5%,scaffold<300,属于高质量基因组草图,满足后续分析要
对不同分离源菌株的基因组特征进行比较发现(

图1 不同分离源表皮葡萄球菌菌株基因组基本特征比较。A:菌株基因组大小;B:菌株CDs数;C:菌株G+C含量。
Figure 1 Comparison of the basic genomic characteristics of Staphylococcus epidermidis strains from different isolated sources. A: Genome size of the strains; B: Number of CDs of the strains; C: G+C content of the strains.
2.2 ANI分析
为解析表皮葡萄球菌的遗传多样性,本研究对373株表皮葡萄球菌两两之间的ANI值进行了计算。结果如

图2 不同分离源表皮葡萄球菌ANI值聚类热图
Figure 2 Cluster heat map of ANI values of Staphylococcus epidermidis from different isolated sources.
2.3 菌群泛-核心基因集分析
利用Roary软件构建了373株表皮葡萄球菌的核-泛基因

图3 373株表皮葡萄球菌核-泛基因集、相关基因占比及功能基因注释。A:373株表皮葡萄球菌核-泛基因集;B:3种分离源表皮葡萄球菌核心基因,辅助基因及特有基因占比(1:血液源;2:母乳源;3:皮肤源);C:373株表皮葡萄球菌功能基因注释(C:能量生成和转换;D:细胞周期控制、细胞分裂和染色体分裂;E:氨基酸转运及代谢;F:核苷酸转运及代谢;G:碳水化合物转运及代谢;H:辅酶转运及代谢;I:脂质转运及代谢;J:翻译、核糖体结构和生物合成;K:转录;L:复制、重组和修复;M:细胞壁、细胞膜、细胞被膜生物合成;N:细胞运动;O:翻译后修饰,蛋白质转换和伴侣蛋白;P:无机离子转运及代谢;Q:次级代谢物生物合成、转运及催化;R:主要功能预测;S:未知功能;T:信号转导机制;U:细胞内运输、分泌及囊泡运输;V:防御机制)。
Figure 3 Core-pan genome set of 373 strains of Staphylococcus epidermidis, proportion of related genes, and annotation of functional genes. A: Sclerotio-pangene set of 373 strains of Staphylococcus epidermidis; B: The proportion of core genes, helper genes and endemic genes of Staphylococcus epidermidis from three isolated sources (1: Blood source; 2: Milk source; 3: Skin source); C: Annotation of functional genes of 373 strains of Staphylococcus epidermidis (C: Energy production and conversion; D: Cell cycle control, cell division, chromosome partitioning; E: Amino acid transport and metabolism; F: Nucleotide transport and metabolism; G: Carbohydrate transport and metabolism; H: Coenzyme transport and metabolism; I: Lipid transport and metabolism; J: Translation, ribosomal structure and biogenesis; K:Transcription; L: Replication; recombination and repair; M: Cell wall/membrane/envelope biogenesis; N: Cell motility; O: Posttranslational modification, protein turnover, chaperones; P: Inorganic ion transport and metabolism; Q: Secondary metabolites biosynthesis, transport and catabolism; R: General function prediction only; S: Function unknown; T: Signal transduction mechanisms; U:Intracellular trafficking, secretion, and vesicular transport; V: Defense mechanisms).
泛基因集中除去核心基因和特异基因,剩余的基因被称为附属基因,又称非必需基因,可增强菌株的生长优势或加强环境适应
2.4 系统发育树分析
为评估表皮葡萄球菌菌株之间的遗传距离,本研究基于1 267个核心基因采用NJ法构建了系统发育树。如

图4 基于373株表皮葡萄球菌的1 267个核心基因构建的系统发育树。0.01代表比例标尺,分支上的数值代表置信度。
Figure 4 Phylogenetic tree based on 1 267 core genes of 373 strains of Staphylococcus epidermidis. The value of 0.01 represents the sequence deviation value, the number on the branch point represents the confidence value.
2.5 功能基因注释
为了对表皮葡萄球菌的功能基因进行初步研究,本研究基于COG数据库对373株表皮葡萄球菌进行功能基因注释。如
对不同分离源菌株的主要功能进行比较发现,3种分离源的菌株在主要功能上并无显著差异(P>0.05),表明不同分离源的表皮葡萄球菌在主要功能上表现出较高的稳定性。
2.6 耐药基因
为了探究不同分离源菌株在耐药基因携带上的差异,本研究通过耐药基因数据库对373株表皮葡萄球菌基因组进行注释。注释结果显示,373株表皮葡萄球菌共鉴定出13种潜在的耐药基因,且3种分离源菌株在耐药基因数量上存在显著差异(P<0.05,

图5 373株表皮葡萄球菌耐药基因相关信息。A:不同分离源菌株在耐药基因数量上差异分析;B:373株表皮葡萄球菌耐药基因存在与缺失热图(0代表缺失;1代表存在)。
Figure 5 Related information of 373 strains of epidermidis staphylococcus drug resistance genes. A: The number of resistance genes between strains from different isolates; B: Heat map of the presence and deletion of antimicrobial resistance genes in 373 strains of Staphylococcus epidermidis (0 represents missing and 1 represents present).
为了进一步了解菌株耐药基因的分布是否与分离源有关,绘制了耐药基因存在与缺失的热图,结果如
细菌主要通过产生钝化酶、药靶变异、药物外排和膜渗透性改变等4种机制形成耐药性,其中由外排泵介导的耐药性最为普
2.7 毒力基因
Severn

图6 373株表皮葡萄球菌毒力基因相关信息。A:不同分离源菌株在毒力基因数量上差异分析;B:373株表皮葡萄球菌毒力因子存在与缺失热图;0代表缺失,1代表存在。
Figure 6 Related information of 373 strains of Staphylococcus epidermidis virulence genes. A: The differences in the number of virulence genes between strains from different isolates; B: Heat map of the presence and deletion of virulence factors in 373 strains of S. epidermidis; 0 represents missing and 1 represents present.
为了解毒力基因的分布是否与菌株分离源有关,本研究利用表皮葡萄球菌的毒力基因存在与缺失情况绘制了热图(
3 讨论与结论
表皮葡萄球菌广泛存在于皮肤、母乳以及血液中,母乳中的细菌对婴幼儿肠道初始菌群的建立及免疫力的提高起到至关重要的作用。然而,目前关于母乳源表皮葡萄球菌的遗传背景和功能基因的研究相对较少。本研究通过对3种分离源共373株表皮葡萄球菌进行比较基因组学研究,发现不同分离源的表皮葡萄球菌在诸多方面存在显著差异。系统发育树结果显示,373株表皮葡萄球菌可分为2个分支且呈现聚集特性,其中体内分离源(母乳源和血液源)菌株的亲缘关系更近。表皮葡萄球菌为适应不同环境而发生了适应性进化,主要体现在基因组大小、CDs数量、附属基因、毒力因子及耐药基因等方面。在毒力因子和耐药基因分析方面,3种分离源菌株携带毒力因子和耐药基因的数量存在显著差异,均呈现血液源菌株最高、母乳源菌株最少的特点。在生物膜合成相关基因icaA/B/C/D/R上,母乳源菌株的携带率最低(3.2%),皮肤源菌株次之(17.5%)而血液源菌株最高(75.2%)。本研究结果表明,母乳源表皮葡萄球菌相对安全,且表皮葡萄球菌为适应母乳环境发生了适应性进化。
作者贡献声明
赵乾:参与实验方法设计,实际调查研究,实验结果可视化,论文初稿撰写,数据整理与管理;李伟程:参与实验方法设计,软件开发与程序设计;李瑜:研究项目管理;孙佳琦:研究项目管理;钟智:研究资源采集;张和平:研究概念生成,研究资源采集,实验设计验证与核实,研究课题监管与指导,论文审阅与修订,研究项目管理。
利益冲突
作者声明不存在任何可能会影响本文所报告工作的已知经济利益或个人关系。
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