diff --git a/python/obitools3/files/linebuffer.pyx b/python/obitools3/files/linebuffer.pyx
index b0dbaf1..3ac070a 100644
--- a/python/obitools3/files/linebuffer.pyx
+++ b/python/obitools3/files/linebuffer.pyx
@@ -8,13 +8,13 @@ Created on 30 mars 2016
 
 cdef class LineBuffer:
 
-    def __init__(self,object fileobj,int size=100000000):
+    def __init__(self, object fileobj, int size=100000000):
         self.fileobj=fileobj 
         self.size=size
     
     def __iter__(self):
         cdef list buff = self.fileobj.readlines(self.size)
-        cdef str  l
+        cdef object  l   # Can be str or bytes
         
         while buff:
             for l in buff:
diff --git a/python/obitools3/files/universalopener.pxd b/python/obitools3/files/universalopener.pxd
index 7743db6..2c7373b 100644
--- a/python/obitools3/files/universalopener.pxd
+++ b/python/obitools3/files/universalopener.pxd
@@ -2,4 +2,4 @@
 
 from .uncompress cimport CompressedFile
 
-cpdef CompressedFile uopen(str name, mode=?)
\ No newline at end of file
+cpdef CompressedFile uopen(object name, mode=?)
\ No newline at end of file
diff --git a/python/obitools3/files/universalopener.pyx b/python/obitools3/files/universalopener.pyx
index 7c4fdbe..9f0b085 100644
--- a/python/obitools3/files/universalopener.pyx
+++ b/python/obitools3/files/universalopener.pyx
@@ -7,15 +7,16 @@ Created on 25 mars 2016
 '''
 
 from urllib.request import urlopen
+from obitools3.utils cimport tostr
 
 
-cpdef CompressedFile uopen(str name, mode='r'):
+cpdef CompressedFile uopen(object name, mode='rb'):
     cdef CompressedFile c
     
     try:
-        f = urlopen(name)
+        f = urlopen(tostr(name))
     except:
-        f = open(name,mode) 
+        f = open(tostr(name),mode) 
         
     c = CompressedFile(f)
     
diff --git a/python/obitools3/parsers/fasta.pyx b/python/obitools3/parsers/fasta.pyx
index 0a7b6d1..fd169d9 100644
--- a/python/obitools3/parsers/fasta.pyx
+++ b/python/obitools3/parsers/fasta.pyx
@@ -11,89 +11,82 @@ import types
 from obitools3.dms.obiseq cimport Nuc_Seq
 
 
-def fastaIterator(lineiterator, 
-                  int skip=0,
-                  only=None,
-                  firstline=None,
-                  int buffersize=100000000
-                 ):
-    cdef str        ident
-    cdef str        definition
-    cdef dict       tags
-    cdef list       s
-    cdef bytes      sequence
-    cdef int        skipped, ionly, read
-#    cdef OBI_Seq    seq
-    
-    if only is None:
-        ionly=-1
-    else:
-        ionly=int(only)
-
-    if isinstance(lineiterator, (str, bytes)):
-        lineiterator=uopen(lineiterator)        
-    if isinstance(lineiterator, LineBuffer):
-        iterator = iter(lineiterator)
-    else:
-        if hasattr(lineiterator, "readlines"):
-            iterator = iter(LineBuffer(lineiterator, buffersize))
-        elif hasattr(lineiterator, '__next__'):
-            iterator = lineiterator
-        else:
-            raise Exception("Invalid line iterator")
-    
-    skipped = 0
-    i = iterator
-    
-    if firstline is None:
-        line = next(i)
-    else:
-        line = firstline
-        
-    while True:
-        
-        if ionly >= 0 and read >= ionly:
-            break
-                
-        while skipped < skip :
-            line = next(i)
-            try:
-                while line[0]!='>':
-                    line = next(i)
-            except StopIteration:
-                pass
-            skipped += 1
-
-        ident,tags,definition = parseHeader(line)
-        s = []
-        line = next(i)
-            
-        try:
-            while line[0]!='>':
-                s.append(str2bytes(line)[0:-1])
-                line = next(i)
-        
-        except StopIteration:
-            pass
-        
-        sequence  = b"".join(s)
-                
-    #         seq = OBI_Seq(id,
-    #                       sequence,
-    #                       definition,
-    #                       tags=tags,
-    #                       )
-          # TODO Seq object
-        yield { "id"         : ident,
-                "definition" : definition,
-                "sequence"   : sequence,
-                "quality"    : None,
-                "offset"     : None,
-                "tags"       : tags,
-                "annotation" : {}
-              }
-        
-        read+=1
+# def fastaIterator(lineiterator, 
+#                   int skip=0,
+#                   only=None,
+#                   firstline=None,
+#                   int buffersize=100000000
+#                  ):
+#     cdef str        ident
+#     cdef str        definition
+#     cdef dict       tags
+#     cdef list       s
+#     cdef bytes      sequence
+#     cdef int        skipped, ionly, read
+#     
+#     if only is None:
+#         ionly=-1
+#     else:
+#         ionly=int(only)
+# 
+#     if isinstance(lineiterator, (str, bytes)):
+#         lineiterator=uopen(lineiterator)        
+#     if isinstance(lineiterator, LineBuffer):
+#         iterator = iter(lineiterator)
+#     else:
+#         if hasattr(lineiterator, "readlines"):
+#             iterator = iter(LineBuffer(lineiterator, buffersize))
+#         elif hasattr(lineiterator, '__next__'):
+#             iterator = lineiterator
+#         else:
+#             raise Exception("Invalid line iterator")
+#     
+#     skipped = 0
+#     i = iterator
+#     
+#     if firstline is None:
+#         line = next(i)
+#     else:
+#         line = firstline
+#         
+#     while True:
+#         
+#         if ionly >= 0 and read >= ionly:
+#             break
+#                 
+#         while skipped < skip :
+#             line = next(i)
+#             try:
+#                 while line[0]!='>':
+#                     line = next(i)
+#             except StopIteration:
+#                 pass
+#             skipped += 1
+# 
+#         ident,tags,definition = parseHeader(line)
+#         s = []
+#         line = next(i)
+#             
+#         try:
+#             while line[0]!='>':
+#                 s.append(str2bytes(line)[0:-1])
+#                 line = next(i)
+#         
+#         except StopIteration:
+#             pass
+#         
+#         sequence  = b"".join(s)
+# 
+#         yield { "id"         : ident,
+#                 "definition" : definition,
+#                 "sequence"   : sequence,
+#                 "quality"    : None,
+#                 "offset"     : None,
+#                 "tags"       : tags,
+#                 "annotation" : {}
+#               }
+#         
+#         read+=1
 
     
 def fastaNucIterator(lineiterator, 
@@ -102,8 +95,9 @@ def fastaNucIterator(lineiterator,
                      firstline=None,
                      int buffersize=100000000
                     ):
-    cdef str        ident
-    cdef str        definition
+    
+    cdef bytes      ident
+    cdef bytes      definition
     cdef dict       tags
     cdef list       s
     cdef bytes      sequence
@@ -143,7 +137,7 @@ def fastaNucIterator(lineiterator,
         while skipped < skip :
             line = next(iterator)
             try:
-                while line[0]!='>':
+                while line[:1]!=b'>':
                     line = next(iterator)
             except StopIteration:
                 pass
@@ -154,8 +148,8 @@ def fastaNucIterator(lineiterator,
         line = next(iterator)
     
         try:
-            while line[0]!='>':
-                s.append(str2bytes(line)[0:-1])
+            while line[:1]!=b'>':
+                s.append(line[0:-1])
                 line = next(iterator)
         except StopIteration:
             pass
@@ -171,17 +165,6 @@ def fastaNucIterator(lineiterator,
             
         yield seq
         
-#         yield { "id"         : ident,
-#                 "definition" : definition,
-#                 "sequence"   : sequence,
-#                 "quality"    : None,
-#                 "offset"     : None,
-#                 "tags"       : tags,
-#                 "annotation" : {}
-#               }
-        
         read+=1
         
-    
-        
         
\ No newline at end of file
diff --git a/python/obitools3/parsers/fastq.pyx b/python/obitools3/parsers/fastq.pyx
index af88b9b..c92f231 100644
--- a/python/obitools3/parsers/fastq.pyx
+++ b/python/obitools3/parsers/fastq.pyx
@@ -28,7 +28,8 @@ def fastqIterator(lineiterator,
                                         offset,
                                         firstline,
                                         buffersize)
-    
+
+
 def fastqWithQualityIterator(lineiterator, 
                   int skip=0,
                   only=None,
@@ -36,14 +37,14 @@ def fastqWithQualityIterator(lineiterator,
                   firstline=None,
                   int buffersize=100000000
                  ):
+    
     cdef LineBuffer lb
-    cdef str        ident
-    cdef str        definition
+    cdef bytes      ident
+    cdef bytes      definition
     cdef dict       tags
     cdef bytes      sequence
     cdef bytes      quality
-    cdef int        skipped, lines_to_skip, ionly, read
-    cdef int        j
+    cdef int        skipped, lines_to_skip, ionly, read, j
     
     if only is None:
         ionly=-1
@@ -84,9 +85,9 @@ def fastqWithQualityIterator(lineiterator,
             break
         
         ident,tags,definition = parseHeader(hline)
-        sequence  = str2bytes(line[0:-1])
+        sequence  = line[0:-1]
         next(i)
-        quality   = str2bytes(next(i)[0:-1])
+        quality   = next(i)[0:-1]
 
         seq = Nuc_Seq(ident,
                       sequence,
@@ -97,15 +98,6 @@ def fastqWithQualityIterator(lineiterator,
         
         yield seq
 
-#         yield { "id"         : ident,
-#                 "definition" : definition,
-#                 "sequence"   : sequence,
-#                 "quality"    : quality,
-#                 "offset"     : offset,
-#                 "tags"       : tags,
-#                 "annotation" : {}
-#               }
-    
         read+=1
         hline = next(i)
     
@@ -116,8 +108,8 @@ def fastqWithoutQualityIterator(lineiterator,
                   firstline=None,
                   int buffersize=100000000
                  ):
-    cdef str        ident
-    cdef str        definition
+    cdef bytes      ident
+    cdef bytes      definition
     cdef dict       tags
     cdef bytes      sequence
     cdef bytes      quality
@@ -163,7 +155,7 @@ def fastqWithoutQualityIterator(lineiterator,
             break
        
         ident,tags,definition = parseHeader(hline)
-        sequence  = str2bytes(line[0:-1])
+        sequence  = line[0:-1]
         next(i)
         next(i)
                 
@@ -175,15 +167,6 @@ def fastqWithoutQualityIterator(lineiterator,
                       tags=tags)
         
         yield seq
-
-#         yield { "id"         : ident,
-#                 "definition" : definition,
-#                 "sequence"   : sequence,
-#                 "quality"    : None,
-#                 "offset"     : None,
-#                 "tags"       : tags,
-#                 "annotation" : {}
-#               }
     
         read+=1
         hline = next(i)
diff --git a/python/obitools3/parsers/header.pxd b/python/obitools3/parsers/header.pxd
index ffcd3cf..423c4d9 100644
--- a/python/obitools3/parsers/header.pxd
+++ b/python/obitools3/parsers/header.pxd
@@ -1,4 +1,4 @@
 #cython: language_level=3
 
 
-cpdef tuple parseHeader(str header)
+cpdef tuple parseHeader(bytes header)
diff --git a/python/obitools3/parsers/header.pyx b/python/obitools3/parsers/header.pyx
index 67fd0a6..cb0261a 100644
--- a/python/obitools3/parsers/header.pyx
+++ b/python/obitools3/parsers/header.pyx
@@ -10,25 +10,25 @@ from obitools3.utils cimport __etag__
 import re
 
 
-__ret__  = re.compile('''(([^ ]+)=('[^']*'|"[^"]*"|[^;]+); *)+?''')
+__ret__  = re.compile(b'''(([^ ]+)=('[^']*'|"[^"]*"|[^;]+); *)+?''')
 
 
-cpdef tuple parseHeader(str header):
-    cdef list m 
-    cdef dict tags 
-    cdef str definition
-    cdef str ident
-    cdef str second
+cpdef tuple parseHeader(bytes header):
+    cdef list  m 
+    cdef dict  tags 
+    cdef bytes definition
+    cdef bytes ident
+    cdef bytes second
     
     m=header[1:-1].split(maxsplit=1)
    
     ident=m[0]
-    if ident[-1] == ';':
+    if len(ident)>1 and ident[-2:-1] == b';':
         ident = ident[:-1]
     
     if len(m)==1:
         tags={}
-        definition='' 
+        definition=b'' 
     else:
         second=m[1]
         m = __ret__.findall(second)
diff --git a/python/obitools3/parsers/ngsfilter.pyx b/python/obitools3/parsers/ngsfilter.pyx
index bdaea16..ce841b1 100644
--- a/python/obitools3/parsers/ngsfilter.pyx
+++ b/python/obitools3/parsers/ngsfilter.pyx
@@ -7,7 +7,6 @@ Created on march 8th 2018
 '''
 
 from .tab import tabIterator
-from obitools3.utils cimport bytes2str
 import types
 
 
@@ -24,18 +23,10 @@ def ngsfilterIterator(lineiterator,
                       ):
     
     cdef list  all_lines
-    cdef str   header 
-    cdef str   sep_str
+    cdef bytes header 
     cdef bytes out_sep
-    cdef str   out_sep_str
         
     out_sep = b"\t"
-    out_sep_str = "\t"
-    
-    if sep is not None:
-        sep_str = bytes2str(sep)
-    else:
-        sep_str = None
 
     if isinstance(lineiterator, (str, bytes)):
         lineiterator=uopen(lineiterator)        
@@ -56,20 +47,20 @@ def ngsfilterIterator(lineiterator,
         all_lines.insert(0, firstline)
         
     # Insert header for column names
-    column_names = ["experiment", "sample", "forward_tag", "reverse_tag", "forward_primer", "reverse_primer"]
-    header = out_sep_str.join(column_names)
+    column_names = [b"experiment", b"sample", b"forward_tag", b"reverse_tag", b"forward_primer", b"reverse_primer"]
+    header = out_sep.join(column_names)
     
     new_lines.append(header)
         
     for line in all_lines:
-        split_line = line.split(sep_str)
+        split_line = line.split(sep)
         tags = split_line.pop(2)
-        tags = tags.split(":")
+        tags = tags.split(b":")
         if len(tags) == 1:          # Forward and reverse tags are the same
             tags.append(tags[0])
         split_line.insert(2, tags[0])
         split_line.insert(3, tags[1])
-        new_lines.append(out_sep_str.join(split_line[0:6]))
+        new_lines.append(out_sep.join(split_line[0:6]))
     
     return tabIterator(iter(new_lines),
                        header = True,
diff --git a/python/obitools3/parsers/tab.pyx b/python/obitools3/parsers/tab.pyx
index fda8385..a2fcb7d 100644
--- a/python/obitools3/parsers/tab.pyx
+++ b/python/obitools3/parsers/tab.pyx
@@ -7,7 +7,6 @@ Created on feb 20th 2018
 '''
 
 import types
-from obitools3.utils cimport bytes2str, tobytes
 from obitools3.utils cimport __etag__
 
 
@@ -28,17 +27,9 @@ def tabIterator(lineiterator,
     cdef int        lines_to_skip, ionly, read
     cdef list       data
     cdef dict       view_line
-    cdef str        sep_str    # TODO can't we read file lines as bytes?
     cdef list       keys
     cdef list       key_types
-    
-    if sep is not None:
-        sep_str = bytes2str(sep)
-    else:
-        sep_str = None
-
-    commentchar_str = bytes2str(commentchar)
-    
+        
     keys = []
     key_types = []
     skipped = 0
@@ -68,7 +59,7 @@ def tabIterator(lineiterator,
     
     while True:
         
-        if (not line.strip() and blanklineskip) or line[0] == commentchar_str:
+        if (not line.strip() and blanklineskip) or line[:1] == commentchar:
             line = next(iterator)
         
         if ionly >= 0 and read >= ionly:
@@ -77,13 +68,13 @@ def tabIterator(lineiterator,
         if not keys:
             if header:
                 # TODO read types eventually
-                keys = line.split(sep_str)
-                keys = [tobytes(x.strip()) for x in keys]
+                keys = line.split(sep)
+                keys = [x.strip() for x in keys]
                 line = next(iterator)
                 continue
             else:
                 # TODO ??? default column names? like R?
-                keys = [str(i) for i in range(len(line.split(sep_str)))]
+                keys = [i for i in range(len(line.split(sep)))]
                 
         while skipped < skip :
             line = next(iterator)
@@ -92,7 +83,7 @@ def tabIterator(lineiterator,
         view_line = {}
         
         # Parse
-        data = line.split(sep_str)
+        data = line.split(sep)
 
         if stripwhite or key_types:
             data = [x.strip() for x in data]
diff --git a/python/obitools3/parsers/universal.pyx b/python/obitools3/parsers/universal.pyx
index 10f7c37..8e90dd7 100644
--- a/python/obitools3/parsers/universal.pyx
+++ b/python/obitools3/parsers/universal.pyx
@@ -5,10 +5,11 @@ from obitools3.parsers.fasta import fastaNucIterator
 from obitools3.parsers.fastq import fastqIterator
 from obitools3.parsers.tab import tabIterator
 from obitools3.parsers.ngsfilter import ngsfilterIterator
+from obitools3.parsers.embl import emblIterator
 
 
-oligore = re.compile("^[ACGTRYSWKMBDHVN]+$",re.I)
-tagre   = re.compile("^([ACGTRYSWKMBDHVN]+|-)(:([ACGTRYSWKMBDHVN]+)|-)?$",re.I)
+oligore = re.compile(b"^[ACGTRYSWKMBDHVN]+$",re.I)
+tagre   = re.compile(b"^([ACGTRYSWKMBDHVN]+|-)(:([ACGTRYSWKMBDHVN]+)|-)?$",re.I)
 
 def is_ngsfilter_line(line):    # TODO doesn't work?
     try:
@@ -16,8 +17,8 @@ def is_ngsfilter_line(line):    # TODO doesn't work?
         ok = tagre.match(parts[2])
         ok&= oligore.match(parts[3])
         ok&= oligore.match(parts[4])
-        ok&= parts[5]=="F" | parts[5]=="T"
-        return ok  
+        ok&= parts[5]==b"F" | parts[5]==b"T"
+        return ok
     except:
         return False
 
@@ -55,19 +56,22 @@ def entryIteratorFactory(lineiterator,
 
     format=b"tabular"
     
-    if first[0]==">":
-        format=b"fasta"
-    if first[0]=="@":
-        format=b"fastq"
-    elif first[0:3]=='ID ':
-        format=b"embl"
-    elif first[0:6]=='LOCUS ':
-        format=b"genbank"
-    elif first[0:11]=='#@ecopcr-v2':   # TODO v2????
-        format=b"ecopcrfile"
-    elif is_ngsfilter_line(first):
-        format=b"ngsfilter"
-        
+    try: 
+        if first[:1]==b">":
+            format=b"fasta"
+        if first[:1]==b"@":
+            format=b"fastq"
+        elif first[0:3]==b'ID ':
+            format=b"embl"
+        elif first[0:6]==b'LOCUS ':
+            format=b"genbank"
+        elif first[0:11]==b'#@ecopcr-v2':   # TODO v2????
+            format=b"ecopcrfile"
+        elif is_ngsfilter_line(first):
+            format=b"ngsfilter"
+    except IndexError:
+        pass
+            
     # TODO Temporary fix
     first=None
     lineiterator.seek(0)
@@ -114,6 +118,14 @@ def entryIteratorFactory(lineiterator,
                                       firstline=first,
                                       buffersize=buffersize),
                     dict)
+
+    elif format==b'embl':
+            return (emblIterator(lineiterator, 
+                                 skip=skip,
+                                 only=only,
+                                 firstline=first,
+                                 buffersize=buffersize),
+                    dict)
     
     raise NotImplementedError('File format not yet implemented')
 
diff --git a/python/obitools3/utils.pxd b/python/obitools3/utils.pxd
index 4d9849d..0673af4 100644
--- a/python/obitools3/utils.pxd
+++ b/python/obitools3/utils.pxd
@@ -14,4 +14,4 @@ cdef obitype_t update_obitype(obitype_t obitype, object new_value)
 cdef obitype_t get_obitype_iterable_value(object value)
 cdef obitype_t get_obitype(object value)
 
-cdef object __etag__(str x)
+cdef object __etag__(bytes x)
diff --git a/python/obitools3/utils.pyx b/python/obitools3/utils.pyx
index 5d0bb83..d75225b 100644
--- a/python/obitools3/utils.pyx
+++ b/python/obitools3/utils.pyx
@@ -160,10 +160,10 @@ cdef obitype_t get_obitype(object value) :
         return get_obitype_single_value(value)
 
 
-__re_int__      = re.compile("^[+-]?[0-9]+$")
-__re_float__    = re.compile("^[+-]?[0-9]+(\.[0-9]*)?([eE][+-]?[0-9]+)?$")
-__re_str__      = re.compile("""^"[^"]*"|'[^']*'$""")
-__re_dict__     = re.compile("""^\{\ *
+__re_int__      = re.compile(b"^[+-]?[0-9]+$")
+__re_float__    = re.compile(b"^[+-]?[0-9]+(\.[0-9]*)?([eE][+-]?[0-9]+)?$")
+__re_str__      = re.compile(b"""^"[^"]*"|'[^']*'$""")
+__re_dict__     = re.compile(b"""^\{\ *
                                    (
                                        ("[^"]*"|'[^']*')
                                         \ *:\ *
@@ -181,9 +181,9 @@ __re_dict__     = re.compile("""^\{\ *
                                        )
                                     )*\ *\}$""", re.VERBOSE)
 
-__re_val__ = re.compile("""(("[^"]*"|'[^']*') *: *([^,}]+|"[^"]*"|'[^']*') *[,}] *)""")
+__re_val__ = re.compile(b"""(("[^"]*"|'[^']*') *: *([^,}]+|"[^"]*"|'[^']*') *[,}] *)""")
 
-cdef object __etag__(str x):
+cdef object __etag__(bytes x):
     cdef list elements
     cdef tuple i
     
@@ -193,11 +193,11 @@ cdef object __etag__(str x):
         v=float(x)
     elif __re_str__.match(x):
         v=x[1:-1]
-    elif x=='None':
+    elif x==b'None':
         v=None
-    elif x=='False':
+    elif x==b'False':
         v=False
-    elif x=='True':
+    elif x==b'True':
         v=True
     elif __re_dict__.match(x):
         elements=__re_val__.findall(x)